Based on 75-g oral glucose tolerance test results from the second National Health and Nutrition Examination Survey (1976-1980), women 20-44 years reporting the use of oral contraceptives (OCs) had decreased glucose tolerance compared with women not using OCs in this age group. Estimates of decreased glucose tolerance after adjustment for age and body mass index were 15.4% (95% CI, 7.6-23.2%) in OC users vs 6.3% (95% CI, 4.5-8.1%) in nonusers. Oral contraceptive use was associated with elevations in 1 and 2 hour plasma glucose concentrations. The mean adjusted difference between OC users and nonusers at 1 and at 2 hours postchallenge was 14 and 13 mg/100 ml, respectively. Characteristics of study nonrespondents vs respondents were analyzed to estimate potential bias due to nonresponse. No appreciable biases were found, but this does not rule out the possibility that some bias may exist.