Twenty women suffering from a polycystic ovary syndrome (PCO) accompanied by hirsutism were given a low-dose oral contraceptive combination containing 0.150 mg desogestrel plus 0.030 mg ethinylestradiol for 8 months. The pretreatment situation regarding hair and hormone profiles in the PCO group was compared with that in 22 regularly menstruating women. Serum levels of free and total testosterone and androstenedione were significantly elevated in PCO women, as were body weight, blood pressure, hair diameter and depilation frequency. Sex hormone binding globulin (SHBG) binding capacity was lower. Following treatment of the PCO group for 8 months, total and free testosterone levels were depressed, but androstenedione had not changed significantly. SHBG binding capacity was increased five-fold. Body weight decreased in the obese women. Hair growth was significantly suppressed and the hair itself was less coarse. Depilation intervals were longer. Acne, present before the treatment had now disappeared. Blood pressure did not change. Few and mild side effects were recorded. After treatment, 3 women succeeded in becoming pregnant and in 8 others spontaneous menstruations had recurred.