Factors related to six respiratory and cardiovascular symptoms have been studied in a sample of 1229 apparently healthy men aged 40-65 working in two factories in West Central Scotland and in a general population sample of 1408 men aged 40-65 living in the same area. The objective was to compare the prevalence of these symptoms in the two samples in relation to major risk factors as identified in a multi-phasic investigation linked to the Mid-Span screening programme. The comparison for cardiorespiratory health and cardiorespiratory function is based on a self-completed questionnaire and a series of physical examinations. The following factors were assessed by multiple regression: age, occupational status, exercise, smoking habit, respiratory symptoms and signs, blood pressure, serum cholesterol and electrocardiogram. The result showed that employees in the two factories had lower prevalence of cardiorespiratory symptoms and better risk profiles than the general population sample. Significant correlations were obtained between respiratory symptoms and cardiac disabilities in both groups. The other risk factors studied were not predictive of cardiac disability in either. Comparison was also made between signs and symptoms detected at screening. The FEV% was significantly correlated with the prevalence of symptoms of bronchitis, dyspnoea and angina in the general population but less so in the occupational group. Severe E.C.G. abnormalities were predictive of angina and possible myocardial infarction in the general population but not in the occupational group. Cigarette smoking was significantly associated with increased prevalence of most cardiorespiratory symptoms studied.