Background. Obesity and non-insulin-dependent diabetes mellitus (NIDDM) have increased in prevalence in Polynesian Western Samoans over the 13-year period 1978-1991, as the population undergoes an 'epidemiological transition'. Methods. We therefore investigated changes in the frequency of dyslipidaemia over the same period in adults aged 25-74 years, and examined factors associated with dyslipidaemia in cross-sectional and longitudinal data. Subjects were drawn from three geographically defined locations representing different degrees of modernization. Results. The age-standardized prevalence of dyslipidaemia increased in each location between 1978 (n = 1197) and 1991 (n = 1748), with the prevalence of hypercholesterolaemia (≤ 5.5 mmol/l) increasing from 18% to 36% (P < 0.001), and that of hypertriglyceridaemia (≤ 2.0 mmol/l) increasing from 9% to 15% (P < 0.001) in the capital city, Apia. In 1991 the highest serum concentrations of total, high density lipoprotein (HDL) and calculated low density lipoprotein (LDL) cholesterol were found in Poutasi (intermediate level of modernization), and the highest triglyceride levels in urbanized Apia. Higher levels of body mass index (BMI), waist-hip ratio (WHR), glucose intolerance, fasting insulin concentration, physical inactivity, educational level, and occupational status were all associated with adverse lipid levels in univariate data. Obesity (BMI in women, WHR in men) and survey location were the most important correlates of abnormal lipid levels in logistic regression models. Fasting insulin was also independently associated with high triglyceride levels in men, while in women the increasing levels of fasting insulin were associated with adverse levels of total, LDL and HDL cholesterol, and triglycerides. In longitudinal data (n = 311), lower baseline levels of cholesterol and triglycerides were associated with greater increases in either parameter at follow-up. Elevated fasting insulin and female gender also predicted increasing cholesterol concentrations, and urban residence predicted an increase in triglyceride levels. Conclusions. Current levels of dyslipidaemia in Western Samoa are similar to those observed in developed Western populations, and are increasing rapidly. These findings, considered along with the high prevalence of other cardiovascular disease risk factors in Samoans, including smoking, obesity and NIDDM, suggest that cardiovascular disease will be a major health concern in the future.