Epidemic increases in active syphilis have been reported in the geographic areas hit hard by acquired immunodeficiency syndrome. Although both epidemics have been associated with illicit substance abuse, the extent to which recent increases in syphilis are linked to the human immunodeficiency virus (HIV-1) epidemic is uncertain. In order to define the frequency of syphilis and HIV-1 coinfection in the pregnant patients seen at City Hospital Center at Elmhurst, we saved syphilis-positive serologic specimens from obstetrical patients for anonymous HIV-1 antibody testing. Of 120 women who tested positive for syphilis, 7/120 (5.8%) had antibodies to HIV-1; of the 44 women with VDRL titers greater than or equal to 1:16 (suggestive of a recent infection), 1/44 (2.3%) had antibodies to HIV-1.