PIP: Data on 146 Mexican women aged 20-44 years who were residents of the Mexico City metropolitan area, married or in stable union, and who suffered from nonrheumatic cardiovascular disease, and on 387 controls matched for age, parity, and education were used to study the possible association of nonrheumatic cardiovascular diseases and the use of oral contraceptives (OCs). The women were hospitalized at Mexican Institute of Social Security hospitals between 1979 and 1982. 20 cases had ischemic heart disease, 15 had cerebrovascular accidents, 50 had pulmonary embolism or venous thrombosis, 27 had hypertensive cardiopathy, and 41 had other conditions, primarily arrhythmia, cardiomyopathies, and pericarditis. Among OC users and controls respectively, 1.3% and 2.3% had never been pregnant. 35.0% and 18.6% were aged 20-29 years, 50.0% and 49.0% were 30-39, and 15.0% and 32.4% were 40-44. 25.0% of users and 22.8% of nonusers currently smoked. 60.0% of users and 76.5% of nonusers had primary education or less. The relative risk for nonrheumatic cardiovascular disease was 1.00 for 58 women who had never used OCs, 1.49 for 88 ever-users of OCs, and 1.40 for 26 current users. The relative risk for 10 women using pills with an estrogen dose of 40 mcg or less was 1.60, compared to 1.06 for 11 women with an estrogen dose over 40 mcg. The relative risk was 1.60 for 52 patients using OCs for 12 months or less, 1.13 for 22 patients using them for 13-48 months, and 1.87 for 14 patients using them for over 48 months. Relative risk increased by age and was over 3 times as high for women aged 40-44. The relative risk was 1.55 for 13 OC users who had never smoked, .44 for 2 users who had previously smoked, and 1.51 for 11 users who currently smoked. Considering smoking only, relative risk was 1.00 for 80 women who never smoked, 1.61 for 66 who previously smoked, and 1.45 for 47 who currently smoked. The risk was significantly increased in OC users for ischemic heart disease, cerebrovascular accidents, venous thrombosis, and pulmonary thromboembolism.^ieng