Background The HMG CoA reductase inhibitors have quickly become the most widely prescribed family of agents for the treatment of patients with elevated low-density lipoprotein (LDL) cholesterol. The incidence of side effects with these agents increases as the dose increases within the recommended dosage range. A lower dosage presumably would have a lower incidence of adverse effects. In addition, lower doses should translate into reduced drug costs. Methods and Results We compared the efficacy of 10 mg of pravastatin and 10 mg of lovastatin in a randomized, crossover design trial among 30 patients with hypercholesterolemia. At baseline, their total cholesterol and LDL cholesterol levels were 249.0 ± 27.3 and 185.1 ± 25.5 mg/dL. After 4 weeks of treatment with lovastatin, the total cholesterol and LDL cholesterol levels fell to 202.8 ± 29.6 and 141.0 ± 25.3 mg/dL, decreases of 19% and 24%, respectively. Four weeks of pravastatin treatment resulted in levels of 212.6 ± 30.8 and 150.5 ± 25.5 mg/dL, or 15% and 19%, respectively. Conclusions There were highly significant changes in total cholesterol and LDL cholesterol levels with each agent and no differences in effect between the 2 agents. In 13 (43%) of the 30 patients, LDL levels were reduced to ≤130 mg/dL with one of the agents. Both agents were generally well tolerated, with no clinically important change in liver function tests or creatinine kinase levels. (Am Heart J 1999;137:458-62.)