As part of a multicentre collaborative study of risk factors for cardiovascular disease (CVD) in the International Clinical Epidemiology Network (INCLEN), each of 12 Centres in 7 countries examined the relationship between CVD risk factors and socio-economic variables. Each Centre (three in Thailand, two each in China, Chile and Brazil and one each in the Philippines, Indonesia and Colombia) examined approx. 200 men aged 35-65 drawn at random from a population within their locality (not designed to be necessarily representative of the general population). Standardized measures of CVD risk factors included body mass index (BMI), blood pressure, blood cholesterol and cigarette smoking habits. Education, occupation and current income were grouped into ordinal categories of socio-economic status according to standard protocol guidelines, and comparisons were made between risk factor levels within each of these categories. Many of these populations had higher levels of education (as a marker of socio-economic status) than would the general population of their country. For both BMI and blood cholesterol there were a number of centres which showed positive associations with socio-economic status. These were predominately in China or urban or rural South East Asia. For blood pressure and cigarette smoking the associations with socio-economic status tended to be negative, more in line with the direction of association seen in the "Developed" World. The high risk factor levels found in these populations, particularly the alarming prevalence of cigarette smoking in Asia and the high cholesterol levels in Latin America and Urban S.E. Asia suggest that CVD will emerge as a major public health problem in the Developing World.(ABSTRACT TRUNCATED AT 250 WORDS)