We investigated 95 Brazilian adults, aged 21-79 years, who were divided into two groups defined as having high-density lipoprotein (HDL)-cholesterol concentrations above [hyperalphalipoproteinaemia (HALP); n=48] or below (controls; n=47) the 90th percentile of a local population. The activities of lipid transfer proteins and enzymes involved in the plasma reverse cholesterol transport and the prevalence of factors that modulate HDL metabolism (alcohol consumption, ponderosity, physical exercise, menopause and use of hormone replacement treatment in women and smoking) were measured, as well as the prevalence of cardiovascular disease and of its various risk factors. The two groups showed no differences in their frequencies of cardiovascular disease. The HDL2/HDL3-cholesterol and triacylglycerol (triglyceride) ratios and the activities of the phospholipid transfer protein (PLTP) and cholesteryl ester transfer protein (CETP) were similar in both groups. Lipoprotein lipase (LPL) and hepatic lipase (HL) activities were 35% higher (P=0.0002) and 40% lower (P=0.0006) respectively, in HALP compared with control subjects. In a multivariate analysis, HDL-cholesterol and its subfractions were influenced by LPL, apolipoprotein A-I, age (negative relationship) and body mass index (negative relationship). Use of alcohol and ponderosity, as well as the interaction of these factors, explained the LPL activity. HL activity was modulated by smoking, and hormone-replacement therapy influenced the apolipoprotein A-I concentration. CETP activity was influenced by race and PLTP by age. The unique phenotype found in this Brazilian HALP population, namely low HL and high LPL activities, could be determined mostly by genetic components, on which future work will focus.