Objective: To examine the relation between body mass index ([BMI] calculated as weight in kilograms divided by the square of height in meters) and the use of medical care services among a nationally representative sample of women. Design and Setting: Multistage cluster-area probability sampling survey. Data are from the Cancer Control and Health Insurance supplements of the 1992 National Health Interview Survey conducted by the National Center for Health Statistics. Respondents were 6981 women aged 18 years or older residing in the United States who self-reported sociodemographic information and the use of health care services. Main Outcome Measures: Interval (≤3 years vs >3 years) since most recent mammography, clinical breast examination, gynecologic examination, and Papanicolaou smear and the number of physician visits in the year before the survey. Results: When age, race, income, education, smoking, and health insurance status were adjusted for, the BMI was directly related to delaying clinical breast examinations, gynecologic examinations, and Papanicolaou smears. Obese women (BMI of 35) were more likely than nonobese women (BMI of 25) to delay clinical breast examinations (odds ratio, 1.26; 95% confidence interval, 1.00-1.58), gynecologic examinations (odds ratio, 1.39; 95% confidence interval, 1.15-1.69), and Papanicolaou smears (odds ratio, 1.29; 95% confidence interval, 1.04-1.58). The BMI was not significantly related to delays in mammography. It was also related to increased physician visits (P = .001). Conclusion: Among women, an increased BMI is associated with decreased preventive health care services, which may exacerbate or even account for some of the increased health risks of obesity.