The diagnosis of 17-ketoreductase deficiency is established in most patients at or after puberty when basal plasma androstenedione levels are high; data on prebubertal children are limited. Two infants with external female genitalia presented in infancy with inguinal herniae and palpable gonads. Both had a 46, XY karyotype, a short vagina, absent uterus, and a gonadal biopsy showing testicular tissue. The value of an hCG stimulation test in making the diagnosis of 17-ketoreductase deficiency was confirmed by a minimal plasma testosterone but marked androstenedione response. Androgen receptor deficiency based on studies in genital skin fibroblasts was demonstrated in one of the cases. We speculate that this is possibly the result of failed induction of receptors secondary to androgen deficiency. Though ‘tomboyish’ in behaviour, both children are reared as girls.