OBJECTIVES. To investigate the relationship between gonadal function, insulin and psychosocial stress in middle-aged men. DESIGN. A population-based, cross-sectional, observational study. SETTING. Glostrup Hospital, Copenhagen, Denmark. SUBJECTS. Four hundred and thirty-nine males, all aged 51 years. MAIN VARIABLES. Body-mass index (BMI), waist-to-hip ratio (WHR), insulin, C-peptide, free testosterone, luteinizing hormone (LH), lipids, fibrinogen, lung function tests (FVC, FEV1, PEF), blood pressure, a self-administered questionnaire with questions on psychosocial variables, lifestyle and self-rated health. RESULTS. Free testosterone correlated inversely (P