Thirty-one women with severe premenstrual syndrome had low sex hormone binding globulin (SHBG) binding capacities 30.2 +/- 9.4 nmol DHT bound/l. The SHBG binding capacities rose when they were treated with three different doses of progesterone. On 400 mg (17 women) SHBG level was 45.11 +/- 11.80. On 800 mg (8 women) SHBG binding capacity rose to 64.75 +/- 14.30 and on the six women who took 1200 mg progesterone daily SHBG binding capacity was 78.5 +/- 23.10. These results are discussed.