Socioeconomic deprivation and waist circumference were measured in three Scottish MONICA cross-sectional surveys of 2233 men and 2516 women aged 25-64 years in 1989-1995. Means of waist circumference, waist/hip ratio (WHR) and body mass index (BMI) increased with level of deprivation (measured by the Carstairs index) more significantly in women than in men, and more significantly in non-smokers than in current-smokers. Their obesity cases defined by conventional cut-points showed similar patterns of relation to deprivation. There appeared to be more obviously consistent and significant increases in the prevalence of large waist circumference with deprivation for both sexes than in the prevalence of WHR and BMI above the 90th centile. Also there was a more significant trend of increase in waist circumference over time than there was in WHR and BMI for both sexes. Residual case-control analysis, controlling for height, showed a 'dose-response' relationship between deprivation and waist circumference. Compared to the most affluent (the first tertile of the Carstairs score), odds ratio for men in the middle group (the second tertile) adjusted for age, survey year and smoking status was 1.37 (95%CI 1.10-1.70) and in the most deprived (the third tertile) 1.46 (1.17-1.82); and for women 1.22 (0.99-1.50) and 1.81 (1.47-2.23). The study suggests that large waist circumference, increasingly prevalent, is directly related to socioeconomic deprivation, and greater attention should be paid to increasing girth in the socially deprived.