The aim of this study was to detect alpha-thalassemia in beta-thalassemia carriers during prenatal screening. During a 12-year prenatal screening program, a total of 158 couples (3.2%) were diagnosed to be the discordant alpha- and beta-thalassemia carriers. Of the 158 beta-thalassemia partners, seven (4.4%) were found to have co-inheritance of alpha0-thalassemia, and three (1.9%) found to have co-inheritance of alpha(+)-thalassemia. Three pregnancies affected with Hb Bart's hydrops fetalis were terminated in the 158 couples. The results showed that molecular analysis must be used for accurate diagnosis of double heterozygotes in couples presumed to be discordant for alpha- and beta-thalassemia on hematologic testing.