A retrospective analysis of HIV-positive patients admitted to the City Hospital, Edinburgh by 31st December 1992, 7 years after the inception of the HIV clinic, revealed that 373 patients, 72% of them injection drug users (IDUs), had required 2069 admissions (5.5/admitted patient, 3.3/clinic patient or 0.5/clinic patient/year) and had utilized 21,934 bed days (59 bed days/admitted patient, 35 days/clinic patient or 5 bed days/clinic patient/year). The average length of stay (ALOS) was significantly longer for AIDS than HIV (non-AIDS) admissions (14.0 vs 9.5, P < 0.0001) as it was for admissions with a CD200 diagnosis (a CD4 count below 200 cells per mm3 on two consecutive occasions) compared to those without (12.1 vs 10.0 days, P = 0.004). There was no gender effect on ALOS but there was a significant effect of risk activity; homo/bisexuals had a significantly longer ALOS than drug users (P < 0.0001). Homo/bisexual patients with AIDS or a CD200 diagnosis had longer ALOS than drug users (15.7 vs 13 days and 15.8 vs 10.8). By 1992 each member of the clinic was on average utilizing one admission per year and 11.6 bed days per year. The number of admissions in that year for patients without a CD200 or AIDS diagnosis was however low (0.5 and 0.75 admissions/patient/year) compared to patients with an AIDS or CD200 diagnosis (2.6 and 1.6 admissions/patient/year). The annual number of occupied bed days/living patient was greatest for those with AIDS (60 vs 5 days) or with a CD200 diagnosis (23.5 vs 4.1 days).(ABSTRACT TRUNCATED AT 250 WORDS)