OBJECTIVES: Anticardiolipin antibodies are estimated to occur in 2.2% of all pregnancies and areassociated with adverse outcomes including thrombotic events, fetal wastage, intrauterine growth retardation, and preterm delivery. We studied 32 human immunodeficiency virus-seropositive gravidas (1) to determine the prevalence of anticardiolipin antibodies in pregnant women infected with human immunodeficiency virus-1 and (2) to investigate the association between the presence of anticardiolipin antibodies and pregnancy outcome, disease status, and perinatal transmission of human immunodeficiency virus-1. STUDY DESIGN: Serum samples obtained at the first prenatal visit were analyzed for anticardiolipinimmunoglobulin M and immunoglobulin G by enzyme-linked immunosorbent assay. Relevant antepartum, intrapartum, and postpartum data, including maternal CD4+ lymphocyte subsets, human immunodeficiency virus p24 antigen determinations, Venereal Disease Research Laboratory test, hematocrit, platelet counts, and placental pathologic tissue of the anticardiolipin antibody-positive and anticardiolipin antibody-negative groups were compared. RESULTS: Test results for 17 (53%) of patients were positive for anticardiolipin antibody: 4 had onlyimmunoglobulin M, 1 had only immunoglobulin G, and the remaining 12 had both antibodies. The patients in the anticardiolipin antibody-positive group were delivered of infants with a mean gestational age of 39 weeks and mean birth weight of 2983 gm. In the anticardiolipin antibody-negative group 15 deliveries had a mean gestational age of 36.3 weeks and a mean birth weight of 2330 gm. CONCLUSIONS: We conclude that there is a high prevalence of anticardiolipin antibodies in patients whohave human immunodeficiency virus, which is not associated with adverse maternal or neonatal outcome, maternal human immunodeficiency virus status, or perinatal transmission of human immunodeficiency virus-1. ( Am J Obstet Gynecol 1992;167:1080–5.)