Factors influencing the outcome of disease were analysed in 289 adults presenting with AIDS in Barcelona, Spain from January 1986 (31 cases) to December 1987 (258 cases). One hundred and fifty-four (53.3%) were parenteral drug addicts and 100 (34.6%) were male homosexuals. Ninety-six (33.2%) presented with tuberculosis, 148 (51.2%), with other opportunistic infections, 34 (11.7%) with Kaposi's sarcoma, and the remaining 11 with a lymphoma. By February 1988, 144 (49.8%) of the 289 had died, with an actuarial survival probability of 46.7% at 2 years (40.7%-52.7%, 95% confidence interval). The factors selected by the multivariate analysis as independently worsening the prognosis were: having been diagnosed as having AIDS before 1986, being more than 45 years old, not being a parenteral drug addict and presenting with an opportunistic infection other than a tuberculosis or with a malignancy. In conclusion, some factors influencing the prognosis for AIDS patients are very dependent upon the geographical area of the series.