We evaluated the prognostic role of a novel tumour-associated antigen, termed 90K, in a cohort of HIV+ asymptomatic haemophilia patients with known duration of seropositivity and median follow-up of about 7 years. The circulating levels of 90K are higher in HIV+ asymptomatic patients than HIV- controls. The antigen levels remain quite stable over time in non-progressing patients, while they steadily rise in patients evolving to ARC/AIDS. Baseline high 90K levels are predictive of faster progression to ARC/AIDS and shorter survival. We conclude that an elevated 90K serum level is a predictor of poor prognosis in HIV+ asymptomatic haemophiliacs.