We present here the first prenatal diagnosis in beta-sarcoglycan muscular dystrophy. The consultand was an 11-week pregnant mother of a girl diagnosed at the age of 3 years with beta-sarcoglycan muscular dystrophy based on the identification of two nonsense mutations in her beta-sarcoglycan gene and on the absence of beta-sarcoglycan in her muscle biopsy. The direct search for these mutations in the chorionic villus DNA of the fetus showed that the fetus did not inherit her sister mutations and thus, was reported as unaffected. We suggest that direct gene mutation detection is more reliable than linkage or protein study in the prenatal diagnosis of sarcoglycanopathies.