This study compares the effects of cholestyramine (16 g/d) and pravastatin (40 mg/d) on lipoprotein particles defined by their apolipoprotein composition (Lp A-I, Lp A-II:A-I, Lp E:B, and Lp C-III:B). Analysis was performed after 4, 8 and 12 weeks of therapy. Low-density lipoprotein (LDL) cholesterol decreased by 25.1% to 35.0% with cholestyramine and 26.2% to 30.7% with pravastatin, while triglycerides decreased slightly with pravastatin therapy and increased slightly during cholestyramine administration. The fall in cholesterol was mainly due to a decrease in very-low-density lipoprotein (VLDL) and LDL cholesterol; high-density lipoprotein (HDL) cholesterol increased. Apolipoprotein B was reduced dramatically (by 21.7% to 30.5% with cholestyramine and 27.7% to 37.4% with pravastatin). No significant effect on apolipoproteins C-III and E was observed with cholestyramine, while pravastatin reduced these parameters slightly. Apolipoprotein A-I increased during therapy with both drugs, while apolipoprotein A-II was slightly decreased. Although the drugs had nearly the same effects on plasma lipids, their influence on lipoprotein particles defined by their apolipoprotein composition was substantially different. Lp A-II:A-I was increased by both drugs (+8.1% to +41.2% for cholestyramine and +7.2% to +32.6% for pravastatin). Lp A-I was also increased with both drugs, but cholestyramine had a more constant and pronounced effect than pravastatin (+15.1% to + 21.7% for cholestyramine and +1.7% to +13.0% for pravastatin). Lp E:B and Lp C-III:B were consistently decreased by pravastatin (−10.2% to −36.5% for LP E:B and −7.2% to −20.9% for Lp C-III:B), while cholestyramine had variable effects on these particles. The latter increased Lp E:B during the first 8 weeks of therapy (about 2%) and thereafter decreased it (−26.2%). In contrast, no significant effect on Lp C-III:B was observed with cholestyramine. These results may be related to the different actions of the drugs on lipoprotein metabolism and suggest that the lipoprotein particle profile may be used to adapt therapy to the individual.