This four-part series describes the experience with HIV infection at Baragwanath Hospital to December 1990. In this first part we give an overview of the emergence of this disease and of its impact on the hospital. From July 1988 to December 1990, 426 HIV-positive individuals were identified: 58 were women identified in surveys at antenatal and gynaecology clinics, 60 were parents of infected babies or sexual contacts of hospitalised patients, and 30 were not inpatients (mainly patients at Soweto clinics). Of the 278 inpatients, 16 were identified in the latter 6 months of 1988, 54 in 1989 and 208 in 1990. Fifty-one per cent of the patients were in the adult medical wards, 11% in surgery, 20% in paediatrics and 18% in other disciplines. One per cent of sera from Wassermann reaction-positive women in mid-1990 were HIV-positive; this also applied to 1% of antenatal women in late 1990 and 2.7% of women with pelvic inflammatory disease. The HIV antigen assay is a useful adjunctive assay in the evaluation of HIV-antibody-positive children. The false/true-positive ratio of a rapid HIV antibody test was 2:1 initially, but the specificity improved with experience. The use of rapid diagnostic assays for HIV must be restricted to laboratories with experience in reading assays and where definitive follow-up testing is assured.