The sera of 849 Tanzanian pregnant women were tested at delivery for Toxoplasma gondii antibodies with the Sabin-Feldman dye test (DT) and an immunosorbent agglutination assay. A total of 296 (35%) of these women had DT titers greater than 1:4. The percentage of women with dye test titers greater than 1:4 was 34-37% regardless of the individual ages. The rate of positivity for human immunodeficiency virus 1/2 (HIV-1/2) using Western blotting was 11.5%. There was no relationship between prevalence of a positive DT result and HIV infection nor between the intensity of the DT result and HIV infection. Sixty-four parturients had a DT titer of 1:1,000 or more. From 57 newborns of these mothers, cord sera were available and were screened by the DT and the immunosorbent agglutination assay. Seven of these were found to be positive for IgM and/or IgA antibodies. It was concluded that the rate of serologic evidence for prenatal Toxoplasma infection in cord blood samples in the present study of Tanzanian pregnant women was approximately 0.8%.