OBJECTIVE This clinical trial was designed to assess the lipids regulating effects of domestic simvastatin (DS, produced by Chengdu Huayu Pharmaceutical Co.) in patients with hyperlipidemia. METHODS 160 hyperlipidemic patients were randomly divided into 3 groups (A, B and C). Groups A and B were subjected to single-blind trial; group C was for open trial. Group A took DS 10 mg q.n., group B Zocor 10 mg q.n. and group C DS 10 mg q.n. respectively for 8 weeks. All the patients were followed up at the 4th week and 8th week. 155 patients finished the trial with 59 cases in group A, 47 cases in group B and 39 cases in group C. RESULTS At the 4th week, serum total cholesterol (TC) in group A, B and C decreased by 16.88%, 19.23% and 14.10%; serum triglycerides (TG) decreased by 19.27%, 15.66% and 17.96%; HDL-C increased by 7.69%, 7.46% and 6.69%; and LDL-C decreased by 23.02%, 27.84% and 24.43%, respectively; there was no significant difference among the three groups (P > 0.05). At the 8th week, serum TC in groups A, B and C decreased by 25.03%, 26.53% and 25.22%. TG decreased by 23.85%, 24.74% and 24.75%; HDL-C increased by 9.23%, 8.95% and 8.39%; and LDL-C decreased by 33.72%, 35.50% and 30.99%, respectively; still, no significant difference among the three groups was observed (P > 0.05). The incidence rates of side effects in the three groups were similar. The clinical effects were more significant at the 8th week than at the 4th week for Zocor and DS. CONCLUSIONS These data suggest that DS is as effective and safe as Zocor in clinical use for lipids regulating serum.