In the present study, we describe the clinical, endocrinological, psychosexual and biochemical features of 7 Mexican male pseudohermaphrodites with primary 5 alpha-reductase deficiency in whom heterogeneity in the pattern of gender identity change at puberty was observed. The patients belonged to 5 different pedigrees from diverse locations in Mexico. Six of them were admitted to the Hospital during or after puberty. The one prepubertal subject was the sibling of a previously studied patient. Basal serum gonadotropins were determined by double antibody radioimmunoassay. Basal and choriogonadotropin (CG)-stimulated concentrations of androstenedione (A), testosterone (T) and dihydrotestosterone (DHT) were determined by radioimmunoassay after extraction and separation by celite chromatography. Urinary aetiocholanolone, androsterone and C19 and C21 5 beta/5 alpha metabolite ratios were analyzed by capillary gas chromatography. Enzyme activity and androgen receptors were studied in fibroblasts cultured from genital skin. Psychological assessment was performed using the Bender-Gestalt Wechsler Adult Intelligence Scale, the Rorschach Ink Blot and the Thematic Apperception Tests. All 7 patients were unambiguously reared as females; three spontaneously changed their gender identity and role from female to male after puberty, another one changed during psychotherapy at the end of puberty. Two patients (one prepubertal and the other pubertal) have been under therapy during 1.5 years, but due to familial and social factors a female gender has prevailed. The remaining patient consulted at age 15 because of virilization; her female gender identity did not change after more than one year of treatment and due to the fact she was depressed and had suicidal tendencies, the penis and testes were removed.(ABSTRACT TRUNCATED AT 250 WORDS)