Prebeta1-high density lipoprotein (prebeta1-HDL), the initial acceptor of cell-derived cholesterol, can be generated from HDL(2) by hepatic lipase. Because bezafibrate elevates lipase activity, it may increase prebeta1-HDL at the expense of HDL(2). To answer this question, we determined the apolipoprotein A-I (apoA-I) distribution in 20 hypertriglyceridemics (triglycerides>2.26 mmol/L) and 20 sex-matched normolipidemics by native 2-dimensional gel electrophoresis. At baseline, prebeta1-HDL was 70% higher in hypertriglyceridemics than in normolipidemics (123.5+/-49.9 versus 72.5+/-34.1 mg/L apoA-I, P<0.01). Prebeta1-HDL was positively correlated with triglyceride (r=0.624, P<0.0001). A 4-week bezafibrate treatment (400 mg daily) increased prebeta1-HDL by 30% (160.2+/-64.5 mg/L apoA-I, P<0.05) but decreased HDL(2b) by 31% (from 188.8+/-94.9 to 129.3+/-78.7 mg/L apoA-I, P<0.05). Hepatic lipase activity increased by 24% (P<0.005). Prebeta1-HDL was generated either from ultracentrifugally isolated HDL(2) or from plasma during incubation with triglyceride lipase. In conclusion, bezafibrate increases prebeta1-HDL at the expense of HDL(2). We speculate that such an effect might partly contribute to the antiatherogenic action of bezafibrate.