A simplified enzymic procedure to determine accurately serum triglycerides is described. Serum triglycerides are hydrolyzed completely to free fatty acids and glycerol by lipoprotein lipase from Pseudomonas fluorescens. The released glycerol is oxidized with glycerol dehydrogenase from Erwinia aroideae in the presence of NAD+, were the reduction of the enzyme-linked NAD+ is coupled to the reduction of nitro blue tetrazolium as a chromogenic indicator with phenazine methosulfate serving as an intermediate electron carrier of NADH. The absorbance at 570 nm is measured. The method requies only 20 microliter of serum and a 10-min incubation and is rapid and simple. The present method offers the measurement of a high concentration of triglyceride up to 1000 mg/dl serum. The results obtained by the present method show good correlation with those obtained by the glycerol kinase method (correlation coefficient, 0.989) or the acetylacetone method (correlation coefficient, 0.979). These results suggest that the proposed method will be utilized as a method or routine clinical test.