The efficacy and tolerance of a garlic preparation (Sapec, Kwai) was investigated in a randomized double-blind study vs. bezafibrate. This multi-centre study was conducted in 5 general medical practices and involved 98 patients with primary hyperlipoproteinaemia. The daily doses of the active substances were 900 mg of garlic powder (standardized as to 1.3% alliin) and 600 mg of bezafibrate, respectively. The pre-phase with placebo lasted 6 weeks, the treatment period covered 12 weeks. All patients were advised to observe a low-fat "step-1 diet" for the duration of the study. The 98 case report forms allowed the statistical evaluation of total cholesterol, HDL cholesterol and triglyceride levels for 94 patients, and of LDL cholesterol values for 92 patients. In the course of the treatment both study medications caused a statistically highly significant reduction in total cholesterol, in LDL cholesterol and triglycerides, and an increase in HDL cholesterol. However, there was no significant difference in the efficacies of both medication groups. Side effects were mentioned by 5 patients each in both treatment groups, none of which led to the withdrawal of the patients. Concerning the garlic preparation, there was no correlation between the perception of garlic odour and the influence on the cholesterol level.