The Hangover Part II takes no chances and opts for a safe, subdued pre-wedding brunch. Things do not go as planned, resulting in another bad hangover with no memories of the previous night. Development began in April 2009, two months before "The Hangover" was released. The principal actors were cast in March 2010 to reprise their roles from the first film. Production began in October 2010, in Ontario, California, before moving on location in Thailand. The film was released on May 26, 2011 and became the highest-grossing R-rated comedy during its theatrical run. A third and final installment, "The Hangover Part III", was released
Hangover research of alcohol hangover is growing rapidly. The Alcohol Hangover Research Group had its inaugural meeting in June 2010 as part of the Research Society on Alcoholism (RSA) 33rd Annual Scientific Meeting in San Antonio, Texas. In 2012, Éduc'alcool, a Quebec-based non-profit organization that aims to educate the public on the responsible use of alcohol, published a report noting hangovers have long-lasting effects that inhibit the drinker's capabilities a full 24 hours after heavy drinking. In 2012, Las Vegas based Hangover Heaven, a mobile hangover treatment clinic, opened along with its Hangover Research Institute, which studies the treatment of hangovers.