Elevated blood viscosity is a predictor of cardiovascular disease. The major determinants of blood viscosity are hematocrit and plasma viscosity. Plasma triglycerides elevate plasma viscosity; however, the contribution of plasma triglycerides to blood viscosity after adjustment for other major covariates has not been reported. This cross-sectional study of 257 adult subjects evaluated the associations between fasting plasma lipids, fibrinogen, total serum protein, hematocrit and blood viscosity. Blood viscosity was measured at 37 degrees C with a coaxial cylinder microviscometer at shear rates of 100 and 1 s(-1). Blood viscosity values are reported both as uncorrected measurements and measurements corrected to a hematocrit of 45% by a regression equation. Uncorrected blood viscosity at a shear rate of 100 s(-1) was significantly associated with triglycerides, fibrinogen, high density lipoprotein (HDL) cholesterol, total serum protein, and hematocrit using stepwise multivariate regression analysis. When corrected blood viscosity at 100 s(-1) was the dependent variable, there were statistically significant associations with triglycerides, HDL cholesterol, and total serum protein. Corrected blood viscosity at 1 s(-1) was significantly associated with triglycerides, fibrinogen, total serum protein, and an indicator variable for diabetes mellitus. This study supports an additional mechanism whereby triglycerides may contribute to cardiovascular risk.