Cytochrome P450c17 deficiency is one of the rare forms of enzyme disorders in steroid biosynthesis, resulting from defects in 17alpha-hydroxylase and 17,20-lyase activities. The disease is caused by the mutations in CYP17 gene, inherited in an autosomal recessive pattern. We reported a Chinese family with three sisters suffering from P450c17 deficiency based on their clinical features and molecular genetics. The patients were found to be compound heterozygotes with two different mutations. Screened by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP), a heterozygous point mutation His373Leu was detected in the exon 6 of CYP17 gene which was proved to be derived from paternal allele. The other allele contained nine-base pair deletion, located in exon 8, eliminating codons 487-489 (Asp-Ser-Phe) near the carboxy-terminus of P450c17. The mother and the brother have been demonstrated to be carriers of deletion mutation through restriction enzyme analysis. Both mutations have been reported previously in Asia. This is the first report of the molecular genetic study of 17alpha-hydroxylase/17,20-lyase deficiency in mainland China with a novel compound heterozygous mutation.