The prevalence of HIV/AIDS among people in midlife and late adulthood has been increasing in Western countries over the last decade. We analyzed data from a prospective, observational multi-centre study on individuals newly diagnosed with HIV between January 2004 and March 2007 in 10 public counselling and testing sites in Latium, Italy. At diagnosis, routine demographic, epidemiological, clinical and laboratory data are recorded, and patients are asked to complete a questionnaire investigating socio-demographic and psycho-behavioural aspects. To analyze the association of individual characteristics with age, we compared older adults (> or = 50 years) with their younger counterpart (18-49 years). To adjust for potential confounding effect of the epidemiological, clinical and behavioural characteristics, to identify factors associated with older age at HIV diagnosis, multivariate logistic regression analysis was performed. Overall, 1073 individuals were identified, 125 of whom (11.6%) were aged 50 years or above. The questionnaire was completed by 41% (440/1073). Compared with their younger counterparts, a higher proportion of older patients were males, born in Italy, reported heterosexual or unknown HIV risk exposure, were never tested for HIV before and were in a more advanced stage of HIV infection at diagnosis. In addition, older adults had a lower educational level and were more frequently living with their partners or children. With respect to psycho-behavioural characteristics, older patients were more likely to have paid money for sex and have never used recreational drugs. Interestingly, no differences were found regarding condom use, which was poor in both age groups. These findings may have important implications for the management of older adults with HIV, who should be targeted by appropriate public health actions, such as opportunistic screening and easier access to healthcare. Moreover, strategies including information on HIV and prevention of risk behaviours are needed.