Background Morbidity and mortality of advanced human immunodeficiency virus infection (HIV) have declined in Western industrialized countries since the availability of highly active antiretroviral therapy (HAART). It is unclear if this has also happened in Hong Kong.Methods We studied a retrospective cohort of patients with advanced HIV disease in Hong Kong, China. First, the mortality of advanced HIV disease per year was calculated for the decade 1993 to 2002, both annually and according to patient observation before and after 1997. Second, the event rates were estimated for the clinical end points of acquired immune deficiency syndrome (AIDS) and death. Univariate and multivariate analyses were then performed to identify associated factors. Results The crude mortality of advanced HIV disease declined from 10.8-30.4 per 100 patients during 1993-1996, to 0.8-6.9 per 100 patients during 1997-2002. A rate ratio of 4.04 (95% CI, 2.52-6.47) was evident for those observed in 1993-1996, compared to those in 1997-2002. In a multivariate analysis where calendar period was adjusted, use of highly active antiretroviral therapy was associated with rate ratios of 0.13 (95% CI, 0.05-0.33) for death after AIDS, 0.08 (95% CI, 0.04-0.19) for AIDS after a CD4 cell count <200/μl, and 0.21 (95% CI, 0.07-0.67) for death after CD4 cell count <200/μl. In the same analysis, calendar period ceased to be a significant factor after adjustment for use of HAART.Conclusions The mortality and morbidity of advanced human immunodeficiency virus disease have declined in Hong Kong. This improved prognosis was attributable to the use of highly active antiretroviral therapy. Background Morbidity and mortality of advanced human immunodeficiency virus infection (HIV) have declined in Western industrialized countries from the availability of highly active antiretroviral therapy (HAART). It is unclear if this has also happened in Hong Kong. Methods We studied a retrospective cohort of patients with advanced HIV disease in Hong Kong, China. First, the mortality of advanced HIV disease per year was calculated for the decade 1993 to 2002, both annually and according to patient observation before and after 1997. Second, the event rates were estimated for The clinical end points of acquired immune deficiency syndrome (AIDS) and death. Univariate and multivariate analyzes were performed to identify associated factors. Results The crude mortality of advanced HIV disease declined from 10.8-30.4 per 100 patients during 1993-1996, to 0.8 -6.9 per 100 patients during 1997-2002. A rate ratio of 4.04 (95% CI, 2.52-6.47) was evident for those observed in 1993-1996, comp ared to those in 1997-2002. In a multivariate analysis where calendar period was adjusted, use of highly active antiretroviral therapy was associated with rate ratios of 0.13 (95% CI, 0.05-0.33) for death after AIDS, 0.08 (95% CI , 0.04-0.19) for AIDS after a CD4 cell count <200 / μl, and 0.21 (95% CI, 0.07-0.67) for death after CD4 cell count <200 / μl In the same analysis, calendar period ceased to be a significant factor after adjustment for use of HAART.Conclusions The mortality and morbidity of advanced human immunodeficiency virus have declined in Hong Kong. This improved prognosis was attributable to the use of highly active antiretroviral therapy.