The optimal management of chronic pure red cell aplasia caused by parvovirus B19 (B19-PRCA) in patients with AIDS is unclear. Our purpose was to determine the effects of intravenous immunoglobulin (IVIg) in the treatment of B19-PRCA in patients with AIDS. The patients were eight adults with AIDS admitted during the period 1993-1997. A diagnosis of B19-PRCA was made if all the following criteria were met: 1. Bone marrow biopsy finding of pure red cell aplasia; 2. Detection of parvovirus B19 DNA in serum; and 3. No alternative explanation for PRCA. Initial (induction) therapy was with IVIg 1 g/kg daily for 1-2 days. Relapses were treated with IVIg 1 g/kg for 2 days. Maintenance therapy with IVIg 0.4-1.0 g/kg q 4 weeks was given to those patients who developed a second or subsequent relapse. The patients were followed for a mean of 27 months (range 8-38 months). All patients responded to initial therapy with IVIg. Six patients with CD4 counts < 80 cells/mm3 relapsed. The response was short lived in two patients with a CD4 count < 80 cells/mm3 who were given a single infusion of IVIg 1 g/kg as initial therapy. Four patients were given regular maintenance IVIg therapy following a second or subsequent relapse and remain in remission. Two patients whose CD4 counts were > 300 cells/mm3 remain in continuous unmaintained remission from B19-PRCA for over 8 and 11 months, respectively, following induction therapy with IVIg. AIDS patients with B19-PRCA respond well to therapy with IVIg 2 g/kg given over 2 days. Most patients with CD4 counts of < or = 80 cells/mm3 suffer relapse within six months necessitating retreatment with IVIg; maintenance therapy with IVIg 0.4 g/kg q 4 weeks is effective in preventing relapse of B19-PRCA, and may be cost effective. Routine maintenance therapy is probably not indicated in patients with CD4 counts over 300 cells/mm3. Prospective studies are needed to confirm these findings.