β-Glucuronidase (β-G) and N-acetyl-β-glucosaminidase (NAG) activities in polymorphonuclear leukocytes (PMN) and serum were investigated in hyperlipidemia patients with or without hypertension or obesity. PMN-β-G and PMN-NAG activities were significantly lower in hyperlipidemia patients with hypertension and obesity than in those without these conditions. The data suggested that some functions of PMN were impaired in hyperlipidemia patients with hypertension and obesity. Serum β-G and NAG activities in hyperlipidemia patients were significantly higher than in controls, and increased with increases in serum total cholesterol, triglyceride and atherogenic index. Increases in serum β-G and NAG activities in hyperlipidemia patients, presumably were not related directly to atherosclerosis, but were probably related to metabolic abnormalities accompanying hyperlipidemia.