Objective: To evaluate the effects of habitual physical activity (PA) on the metabolic syndrome (MS) in young adult men and women. Research methods and procedures: Cross-sectional PA data were utilized from 249 women and 237 men, aged 18-40 years in the Fels Longitudinal Study. MS components - abdominal circumference (AC), triglycerides (TG), HDL, blood pressure (BP), and fasting glucose (FG) - were dichotomized according to the National Cholesterol Education Program's Adult Treatment Panel III revised criteria. Leisure, sport, work, and total PA scores were calculated using the Baecke Questionnaire of Habitual Physical Activity. Multiple logistic regression modeling assessed the effects of PA, age, smoking, and BMI on MS status. Results: 26.9% of men and 19.3% of women had MS. For men, MS risk was reduced with increases in both total PA [OR = 0.65 (95% CI: 0.47, 0.90)] and sport PA [OR = 0.40 (95% CI: 0.23, 0.70)]. AC, TG, and HDL values also improved with total and sport PA. Among women, the risk for MS was marginally reduced by total PA [OR = 0.72 (95% CI: 0.50, 1.02)] and HDL levels were increased by both total PA [OR = 0.79 (95% CI: 0.63, 0.98)] and sport PA [OR = 0.54 (95% CI: 0.35, 0.84)]. Discussion: Increased total and sport PA reduces risk for the MS in young men, though not as clearly in young women.