We studied HIV rate in different age populations and whether there has been on-going new infections in Hong Kong, by examining the age characteristics and their temporal trend of reported HIV infections. It was found that people in the age group 25-34 were worst hit by the local epidemic. Ageing cohort effect was not apparent for the age pattern of sexually-acquired infections reported from 1987 to 2000, with the annual median ages ranged from 31.5 to 36 years (regression coefficient 0.14, 95% confidence interval -0.14 to 0.42, P = 0.295). Similar temporal age patterns were observed for individual subgroups of homo-/bisexuals, heterosexuals and female heterosexuals. The findings suggested the occurrence of new HIV infections over the years in Hong Kong, despite maintenance of a low prevalence. Albeit capturing largely prevalent infections, reported HIV/AIDS data could be tapped for understanding the evolving epidemic pattern to better evaluate and target current prevention programmes.