5α steroid reductase 2 (5α SR2) deficiency is an autosomal recessive enzyme defect causing male pseudohermaphroditism (MPH) because of an abnormally low peripheral conversion of testosterone to dihydrotestosterone (DHT), which is required for the normal differentiation of external male genitalia. The present report describes the distribution of 5α steroid reductase gene mutations in the Turkish population in the light of published reports from different centers. Eight Turkish patients from unrelated Turkish families and a large pedigree of one of these patients are also discussed. These patients were followed up at Ankara University Department of Pediatric Endocrinology. The presence of Leu 55 Gln mutation in six patients out of 8 indicates the increased prevalence of this mutation in the Turkish population with different presentations. One patient out of six (patient FG) had a large pedigree of Leu 55 Gln mutation in exon 1. The pedigree of this family with marital consanguinity was very remarkable and extraordinary. A further 85 members of this family were analyzed for exon 1 Leu 55 Gln 5α SR 2 gene mutations. Forty two out of the 85 subjects (49.41%) had this alteration in gene mutation. Thirty-one of them were heterozygous (18 genetic male, 13 genetic female) and 11 of them were homozygous (8 genetic male, 3 asymptomatic female carriers) for this mutation. A trinucleotid deletion at straddling codons 156 and 157 is responsible for a methionize residue at position 157 (Δ Met 157) of 5α SR type 2 gene which was first described in our patient NA. Two additional Turkish patients were reported by different investigators with this rare mutation and this also suggests on increased prevalence of this mutation in the Turkish population. In conclusion Leu 55 Gln mutation in exon 1 seems to be a hot spot in Turkish patients. Hence 5α SR2 gene mutation analysis especially Leu 55 Gln mutation in exon 1 and Δ Met 157 in exon 3, must be evaluated in Turkish patients with male pseudohermaphroditism according to our results and other Turkish patients reported by different investigators. It is important that homozysous asymptomatic female carriers be taken into consideration in this clinical entity especially in closed populations because of the risk of carrying the disease to their offspring.