In this paper beta-globin gene mutations were detected in 452 beta-thalassemia carriers from 13462 unselected individuals (6731 pregnant women and their husbands) who were screened for the beta-thalassemia trait in the Guangzhou area of China. The incidence of beta-thalassemia was calculated as 3.36%. This is higher than found in previous studies performed in southern China. Using reverse dot blot analysis, we found 11 types of mutations and identified the mutations in 446 (98.7%) of the 452 cases. Direct sequencing was carried out on the 6 unknown alleles, and a novel amber mutation in a beta 0-thalassemia gene (beta 37TGG --> TAG) was found in one of them. Thus, the prevalence and spectrum of beta-thalassemia mutations were obtained for this region. Twelve couples were detected at risk for thalassemia, and prenatal diagnosis was carried out in 11 of them. This is the largest number of Chinese subjects studied by DNA analysis to date and is the first report on the prospective diagnostic trial for beta-thalassemia in a Chinese population. In addition, we have performed 80 prenatal diagnoses based on screening for beta-thalassemia retrospectively.