The presence of lipids in postprandial urine was assessed in 116 patients with a history of filariasis and 70 normal individuals using a biochemical autoanalyzer. Urinary triglycerides (TGs) ranging from 10 to 1955 mg/dl were detected in 13 individuals with a history of chyluria, including 3 with TG levels ranging from 233 to 1955 mg/dl and cholesterol levels of 6-35 mg/dl. Three patients who had a filarial history but without chyluria were also found to have urinary TGs (13-15 mg/dl) without detectable cholesterol. Neither TGs nor cholesterol were detected in the urine of normal individuals. Fluctuations in postprandial urine lipid contents were measured by time course determinations of urinary TG and cholesterol in 17 patients with filariasis and a history of chyluria, 16 patients with filariasis and hydrocele and 16 normal individuals. The level of urine lipid excretion was found to increase within 1-4 h postprandially, with urinary TG levels ranging between 7.8 and 1284 mg/h in eight patients and urinary cholesterol levels between 1.2 and 138 mg/h in seven patients with a history of chyluria. To evaluate the origin of the urine lipids in hematochyluria, fish oil containing 360 mg eicosapentaenoic acid (EPA) and 240 mg docosahexaenoic acid (DHA) was prescribed to a patient with hematochyluria. The excretion of EPA and DHA in urine was increased postprandially in the patient, similar to the elevation of urinary TG and cholesterol. The profile of fatty acids from urine samples showed it was of dietary origin. Our results suggest that postprandial urine lipids, especially TG, might be used as markers for the clinical evaluation of chyluria.