In a consecutive series of 41 hirsute women clinically classified as benign androgen excess, only 34% were found to have elevated plasma 'total' testosterone (T), 22% having subnormal sex hormone binding globulin (SHBG). When expressed as the ratio T/SHBG ('free androgen index'), 85% of the patients had values above the normal range. It is concluded that this index is more reliable than total testosterone in assessing androgen status in female patients.