The Hong Kong HIV Cohort Database is an observational cohort including all patients enrolled in 2 HIV specialist clinical services in Hong Kong. Basic demographics, HIV transmission category, and the diagnoses of AIDS were captured using a standardized template. As of December 2006, 2132 HIV cases had been registered in the database, representing two thirds of all reports submitted to the government's surveillance system. Non-Chinese and young females≤24 years were less represented in the cohort. Description of cohort cases was, however, more complete in terms of transmission category and presentation with AIDS-defining illnesses. Overall, Pneumocystis jirovecci, tuberculosis, and systemic mycosis accounted for a majority of AIDS cases within 3 months of HIV diagnosis. There was a gradual rise of HIV positive men having sex with men in the cohort, notably after 2002, an observation also made in other Asian countries.