Risk factors for cataract extraction in a young (less than 60 years of age) urban health maintenance organization population were evaluated in a case-control study. The subjects (72 case-control pairs) subscribed to the Kaiser Permanente Medical Care Program in the San Francisco Bay area and had cataract extraction between 1976 and 1980. All patients had visual acuity of at least 20/40 OU, documented before development of cataracts. Thirty-six (50%) of the 72 cataract extraction patients had at least one known risk factor for cataract formation, including trauma, intraocular inflammation, diabetes mellitus, syphilis, oral or topical steroid use, or previous eye surgery. Male patients were found to be a mean of 4.3 years younger than female patients, and diabetics were found to be a mean of 3.5 years older than nondiabetics. Variables found to be related to cataract extraction in univariate analysis included diagnosis of diabetes mellitus, a family history of cataracts, pulse rate, white blood cell count, and syphilis.