A micromethod is described for isolating and quantifying human very-low-density lipoprotein (VLDL) from 0.1 mL of human serum, by which more than 100 samples can be processed in half a day with a standard ultracentrifuge. Replicate analysis of 10 normal and hyperlipemic samples gave median coefficients of variation of 11.7% for VLDL cholesterol, 5.1% for VLDL triglycerides. Results obtained by micro-ultracentrifugation and enzymic cholesterol measurement agreed closely with those measured with an electrophoretic method (Pearson's r = 0.98). Compared with the established method, on the other hand, lower values were found for both VLDL cholesterol (r = 0.89) and triglycerides (r = 0.97).