Adrenal cortical functional activity was studied in 60 patients with polycystic ovary syndrome (PCOS), by applying the adrenocorticotropic hormone (ACTH) test. A control group comprised 20 healthy women of reproductive age. The ACTH test was ascertained to reveal autosomal recessive enzymopathy (inadequate activity of the enzyme 21-hydroxylase (21-OH)) in patients with PCOS. After the ACTH test, the patients who were carriers for the mutant allele of the 21-OH deficiency gene showed a more significant increase in 17-hydroxyprogesterone and dehydroepiandrosterone sulfate than did those who were no carriers for this mutation and healthy women.