OBJECTIVE: Measures of body size reflect genetic and environmental influences on growth and energy balance. Associations between such measures and risk of schizophrenia have been inconsistent. METHOD: This is a population-based cohort study of 1 347 520 men born in Sweden from 1952 to 1982, with height and body mass index (BMI) data available from conscription records. The Swedish National Hospital Discharge Register was used to identify subjects diagnosed with schizophrenia from 1970 to 2000. RESULTS: Subjects with lower BMI and shorter height had an increased risk of developing schizophrenia. Underweight subjects had an approximately 30% increase in risk compared with normal BMI subjects (adjusted HR = 1.30, 95% CI: 1.20-1.42). Tall subjects had an approximately 15% reduction in risk compared with short subjects (adjusted HR = 0.85, 95% CI: 0.80-0.92). CONCLUSION: Both height and BMI in early adulthood are strongly and inversely associated with risk of schizophrenia. We discuss these findings in relation to possible genetic and nutritional causal mechanisms.