A direct antiglobulin test (DAT) was performed in 70 patients with anti-HIV antibodies (group A: seropositive patients without or with minimal disease and group B: AIDS patients with or without malignancies). A positive DAT was found in 24 of 70 patients (34%, significantly higher compared to 0.1% in healthy controls) and a higher prevalence of positive DAT was observed in group B than in group A patients (55% versus 21% p < 0.01). When comparing DAT-positive and negative patients within the same clinical group, no significant difference is seen in haemoglobin levels. There is no difference in serum bilirubin, haptoglobin or reticulocyte count between DAT-positive and negative patients altogether or in the same clinical group. AZT therapy seems to exert no significant influence on the onset of a positive DAT. The results confirm a high prevalence of positive DAT in patients with HIV antibodies, mainly in worse clinical conditions, and suggest that a positive DAT might be a prognostic factor in the clinical course of the disease.