Chinese researchers conducted a meta-analysis to quantify the effects of soy protein containing isoflavones on lipid profile. Twenty-three eligible RCTs published from 1995 to 2002 were identified from the Pubmed database. Weighted mean effect sizes were calculated for net changes in serum lipid concentrations using fixed-effect or random-effect models. Prespecified subgroup analyses were performed to explore the influence of covariates on net lipid change. Soy protein with isoflavones intake was associated with significant decreases in serum total cholesterol (by 0.22 mmol/l or 3.77%), LDL cholesterol (by 0.21 mmol/l or 5.25%) and triacylglycerols (by 0.10 mmol/l or 7.27%), and significant increases in serum HDL cholesterol (by 0.04 mmol/l or 3.03%). The reductions in total and LDL cholesterol were larger in men than in women. Initial total cholesterol concentrations had a powerful effect on changes in total HDL cholesterol, especially in subjects with hypercholesterolaemia. Studies with intakes > 80 mg showed better effects on the lipid profile. The strongest lowering effects of soy protein containing isoflavones on total cholesterol, LDL cholesterol and triacylglycerol occurred within the short initial period of intervention, whereas improvements in HDL cholesterol were only observed in studies of > 12 weeks’ duration. Tablets containing extracted soy isoflavones did not have a significant effect on total cholesterol reduction.