Steroid 5-alpha-reductase 2 deficiency is an autosomal recessive disorder with clinical spectrum ranges from a male phenotype with hypospadia to a female phenotype with normal wolffian structures. Over 50 different mutations of SRD5A2 gene has been described in affected patients and several mutations were detected in specific populations. DNAs of two 46,XY DSD Indonesian siblings, aged 13 and 18 years old, with clinically suspected of 5-alpha-reductase deficiency and their mother were analysed for molecular defects of SRD5A2 gene. Different from other reports, in our series three mutations were found in each patient. Two novel mutations were detected in these patients and their mother, which are p.Gly34fs and c.699-1G>T. The other mutation detected was c.680G>A or p.Arg227Gln, which commonly described in Far East Asian population. Whether the p.Arg227Gln mutation is considered a polymorphism or a mutation in Indonesian population warrants further study. © Freund Publishing House Ltd., London.