Oxidative stress in diabetes co-exists with a reduction in the antioxidant status, which can further increase the deleterious effects of free radicals. Hyperlipidaemia is one of the major risk factors of cardiovascular complications in diabetes. A study was undertaken to evaluate the antioxidant and antihyperlipidaemic activity of protocatechuic acid (PCA) on streptozotocin (STZ)-induced diabetic rats. The levels of thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides (LOOH) were increased and the level of enzymatic and non-enzymatic antioxidants decreased except vitamin E. Lipid profile increased in diabetic rats, whereas HDL-C level decreased. These alterations reverted to near control levels after the diabetic rats were treated with PCA. Histopathological studies also revealed the protective effects of PCA on liver and kidney. These findings suggest that PCA treatment exerts a therapeutic property by decreasing the oxidative stress and lipid profile. The effect of PCA was comparable to glibenclamide, a well-known hypoglycaemic drug.