OBJECTIVE: Studies directly examining the association between physical activity and NIDDM in African-Americans are rare. Consequently, the strength of this association in this ethnic minority group remains unclear. The current study broadly characterizes the types of physical activity engaged in by a community sample of working-class African-Americans and then quantifies the association between physical activity and NIDDM risk in this population. RESEARCH DESIGN AND METHODS: During the 1993 reexamination of participants in the Pitt County Study in North Carolina, data on NIDDM history, current use of insulin or oral hypoglycemic drugs, and approximately 12-h overnight fasting blood glucose (FBG) were obtained from 598 women and 318 men, ages 30-55 years. The presence of NIDDM was determined by current insulin or medication use and FBG > or = 140 mg/dl. Study participants were assigned to one of four categories of physical activity: strenuous, moderate, low, or inactive. RESULTS: The weighted prevalence of NIDDM in the sample was 7.1%. After adjustment was made for age, sex, education, BMI, and waist-to-hip ratio, NIDDM risk for moderately active subjects was one-third that for the physically inactive subjects (odds ratio [OR], 0.35; 95% CI, 0.12-0.98). The ORs for low (OR, 0.51; 95% CI, 0.20-1.29) and strenuous (OR, 0.65; 95% CI, 0.26-1.63) activity also tended to be lower. A summary OR that contrasted any activity versus no activity was 0.51 (95% CI, 0.23-1.13). CONCLUSIONS: Moderate physical activity was strongly associated with reduced risk for NIDDM in this sample. While replication of these findings is needed, public health interventions designed to increase moderate (leisure-time) physical activity in black adults should be strongly encouraged.