In 56 infertile women, aged 20 to 35, beta-endorphin (beta-EP) was determined out of the sample of peripheral blood plasma as well as the serum testosterone (T), progesterone (Prg), estradiol (E2), dehydroepiandrosterone sulfate (DHEA-S), sex hormone binding globulin (SHBG) at the medium (from the 6th to 9th day) and at the late follicular stage of the menstrual cycle (from the 10th to 14th day), the early luteal stage (from the 15th to 19th day) and at the late luteal stage of the cycle (from the 20th to 25th day). According to the gathered results of T, DHEA-S and the evaluated indexes of free androgenes of--FAI, women were grouped into two groups. Those with hyperandrogenism (n = 30) and those without hyperandrogenism (n = 26), with two subgroups: those with ovulation and those without it. Women with ovulation and without hyperandrogenism showed statistically significant higher concentration of beta-EP at the late luteal stage of the cycle in comparison with those without ovulation belonging to the same group (n = 9; 5.5 +/- 1.4 vs n = 7; 3.5 +/- 0.6; p < 0.01) as well as concerning the early luteal stage of their own cycle (5.5 +/- 1.4 vs 4.3 +/- 0.3; p < 0.5).(ABSTRACT TRUNCATED AT 250 WORDS)