opinion: Mr. Justice Rehnquist
  delivered the opinion of the Court.
  I
  On August 16, 1974, Michael Gilletti, an undercover officer with the Philadelphia Narcotics Squad arranged a heroin “buy” with one Patricia McCafferty (from whom he had purchased narcotics before). McCafferty told him it would cost $115 “and we will go down to Mom Santana’s for the dope.”
  Gilletti notified his superiors of the impending transaction, recorded the serial numbers of $110 (sic) in marked bills, and went to meet McCafferty at a prearranged location. She got in his car and directed him to drive to 2S11 North Fifth Street, which, as she had previously informed him, was respondent Santana’s residence.
  McCafferty took the money and went inside the house, stopping briefly to speak to respondent Alejandro who was sitting on the front steps. She came out shortly afterwards and got into the car. Gilletti asked for the heroin; she thereupon extracted from her bra several glassine envelopes containing a brownish-white powder and gave them to him.
  Gilletti then stopped the car, displayed his badge, and placed McCafferty under arrest. He told her that the police were going back to 2311 North Fifth Street and that he wanted to know where the money was. She said, “Mom has the money.” At this point Sergeant Pruitt and other officers came up to the car. Gilletti showed them the envelope and said “Mom Santana has the money.” Gilletti then took McCafferty to the police station.
  Pruitt and the others then drove approximately two blocks back to 2311 North Fifth Street. They saw Santana standing in the doorway of the house with a brown paper bag in her hand. They pulled up to within 15 feet of Santana and got out of their van, shouting “police,” and displaying their identification. As the officers approached, Santana retreated into the vestibule of her house.
  The officers followed through the open door, catching her in the vestibule. As she tried to pull away, the bag tilted and “two bundles of glazed paper packets with a white powder” fell to the floor. Respondent Alejandro tried to make off with the dropped envelopes but was forcibly restrained. When Santana was told to empty her pockets she produced $135, $70 of which could be identified as Gilletti's marked money. The white powder in the bag was later determined to be heroin.
  An indictment was filed in the United States District Court for the Eastern District of Pennsylvania charging McCafferty with distribution of heroin, in violation of 21 U. S. C. § 841, and respondents with possession of heroin with intent to distribute in violation of the same section. McCafferty pleaded guilty. Santana and Alejandro moved to suppress the heroin and money found during and after their arrests.
  The District Court granted respondents' motion. In an oral opinion the court found that “[t]here was strong probable cause that Defendant Santana had participated in the transaction with Defendant McCafferty.” However, the court continued:
  “One of the police officers . . . testified that the mission was to arrest Defendant Santana. Another police officer testified that the mission was to recover the bait money. Either one would require a warrant, one a warrant of arrest under ordinary circumstances and one a search warrant.”
  The court further held that Santana's “reentry from the doorway into the house” did not support allowing the police to make a warrantless entry into the house on the grounds of “hot pursuit,” because it took “hot pursuit” to mean “a chase in and about public streets.” The court did find, however, that the police acted under “extreme emergency” conditions. The Court of Appeals affirmed this decision without opinion.
  II
  In United States v. Watson, 423 U. S. 411 (1976), we held that the warrantless arrest of an individual in a public place upon probable cause did not violate the Fourth Amendment. Thus the first question we must decide is whether, when the police first sought to arrest Santana, she was in a public place.
  While it may be true that under the common law of property the threshold of one's dwelling is “private,” as is the yard surrounding the house, it is nonetheless clear that under the cases interpreting the Fourth Amendment Santana was in a “public” place. She was not in an area where she had any expectation of privacy. “What a person knowingly exposes to the public, even in his own house or office, is not a subject of Fourth Amendment protection.” Katz v. United States, 389 U. S. 347, 351 (1967). She was not merely visible to the public but was as exposed to public view, speech, hearing, and touch as if she had been standing completely outside her house. Hester v. United States, 265 U. S. 57, 59 (1924). Thus, when the police, who concededly had probable cause to do so, sought to arrest her, they merely intended to perform a function which we have approved in Watson.
  The only remaining question is whether her act of retreating into her house could thwart an otherwise proper arrest. We hold that it could not. In Warden v. Hayden, 387 U. S. 294 (1967), we recognized the right of police, who had probable cause to believe that an armed robber had entered a house a few minutes before, to make a warrantless entry to arrest the robber and to search for weapons. This case, involving a true “hot pursuit,” is clearly governed by Warden; the need to act quickly here is even greater than in that case while the intrusion is much less. The District Court was correct in concluding that “hot pursuit” means some sort of a chase, but it need not be an extended hue and cry “in and about [the] public streets.” The fact that the pursuit here ended almost as soon as it began did not render it any the less a “hot pursuit” sufficient to justify the warrantless entry into Santana's house. Once Santana saw the police, there was likewise a realistic expectation that any delay would result in destruction of evidence. See Vale v. Louisiana, 399 U. S. 30, 35 (1970). Once she had been arrested the search, incident to that arrest, which produced the drugs and money was clearly justified. United States v. Robinson, 414 U. S. 218 (1973); Chimel v. California, 395 U. S. 752, 762-763 (1969).
  We thus conclude that a suspect may not defeat an arrest which has been set in motion in a public place, and is therefore proper under Watson, by the expedient of escaping to a private place. The judgment of the Court of Appeals is
  Reversed.
  An Officer Strohm testified that he recognized Santana, whom he had seen before. He also indicated that she was standing directly in the doorway — one step forward would have put her outside, one step backward would have put her in the vestibule of her residence.
  It is not apparent on what grounds respondent Alejandro had standing to protest the seizures. However, the Government did not raise this issue below and consequently we do not reach it.
  Warden was based upon the “exigencies of the situation,” 387 U. S., at 298, and did not use the term “hot pursuit” or even involve a “hot pursuit” in the sense that that term would normally be understood. That phrase first appears in Johnson v. United States, 333 U. S. 10, 16 n. 7 (1948), where it was recognized that some element of a chase will usually be involved in a “hot pursuit” case.
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