This study assessed whether or not the consumption of soy milk could add significantly to the lipid profile and lipid peroxidation in comparison with non-fat milk. A double-blind, randomised, crossover study was conducted on 60 outpatients with primary hypercholesterolaemia following a lipid-lowering diet for at least 6 weeks. Lipid profile was obtained at baseline and at 6 and 12 weeks, with the patients randomly assigned to receive initially 1 1/day of soy milk or non-fat cow’s milk for 6 weeks. Lipid peroxidation was estimated by plasma thiobarbituric reactive substances. Apolipoprotein E genotypes were examined by polymerase chain reaction restriction fragment length polymorphism. The soy milk diet was associated with LDL-C reduction and with HDL-C increase.