Abnormalities in lipid metabolism have been widely described in cancer-bearing patients and animals. In particular, the presence of the tumor seems to profoundly affect triglyceride (TG) utilization by interfering with lipoprotein lipase (LPL) activity. Exogenous TG plasma clearance was evaluated in 10 nonmalnourished patients with cancers of various origin and 10 normolipidemic volunteers by means of a three-stage intravenous lipid clearance test. This technique allows precise determination of both the fractional removal rate (K2) and the maximal clearing capacity (K1) for exogenous lipids. Mean K2 values (min-1) were found to be significantly reduced in cancer patients compared with control subjects (0.07 +/- 0.006 vs 0.13 +/- 0.013 SEM, p less than 0.005). K1 values (mumol/L/min) were also found to be significantly lower in cancer patients than in the control group (109.43 +/- 6.3 vs 143 +/- 6.3 SEM, p less than 0.01). The data obtained indicate that the capacity to eliminate exogenous lipids from the bloodstream is reduced in cancer-bearing patients. This may be the consequence of a tumor-related impairment of LPL system activity.