SUMMARY Pituitary content or concentration of follicle-stimulating hormone (FSH), prolactin and growth hormone in the genetically androgen insensitive male rat pseudohermaphrodite is intermediate between normal male and female rats, while pituitary luteinizing hormone (LH) concentration and serum FSH levels are the same as in the normal male. The concentration of serum LH, prolactin and growth hormone indicates no sexual dimorphism. Although the pseudohermaphrodite is genetically male with a female phenotype, our results suggest some degree of masculinization of the hypothalamicpituitary system.