The survival pattern was studied for 687 Danish AIDS patients (93% of notified cases in the study period) who were diagnosed with AIDS during the period from 1980 to 1990. The median survival was 17 months. Factors significantly associated with a shortened survival were transfusion-acquired HIV infection, age > 40 years, year of diagnosis before 1987, and the presence of either disseminated infection with Mycobacterium avium-complex, Cytomegalovirus chorioretinitis or malignant lymphoma at time of the AIDS diagnosis. There was also a significant association between survival and CD4 cell count at time of AIDS diagnosis. Patients who had CD4 cell counts above 200 x 10(6)/l had twice as long a survival as patients who had CD4 cell counts less than 50 x 10(6)/l. The prognosis of Danish AIDS patients remains poor. The most important determinant of survival time appears to be the degree of immune deficiency at time of diagnosis.