We estimated the proportion of drug users at treatment centres in Italy who had undergone HIV testing and the correlates of testing. Of the 1,917 drug injectors, 37.4% had been tested in the current year; of the 665 non-injectors, 28% had been tested. Among injectors, testing was associated with: being older than 35, foreign nationality, residing in central Italy, drug use for over 2 years, and having undergone both pharmacological and psychological treatment. Among non-injectors, an association was found for foreign nationality and not having been treated at other facilities. The results stress the need to facilitate access to testing.