Although most US NEPs operate legally, many report some form of police interference. In a 2009 national survey of 111 US NEP managers, 43% reported at least monthly client harassment, 31% at least monthly unauthorized confiscation of clients’ syringes, 12% at least monthly client arrest en route to or from NEP and 26% uninvited police appearances at program sites at least every 6 months. In multivariate modeling, legal status of the program (operating legally vs illegally) and jurisdiction's syringe regulation environment were not associated with frequency of police interference.