A randomized trial was conducted to compare effects of a diet high in monounsaturated fatty acids, enriched with avocado (AE), and a high-complex-carbohydrate diet (AHA-III) on blood lipid concentrations. Fifteen females between 37 and 58 y of age were allocated either to AE followed by AHA-III, or vice versa. Each dietary phase lasted 3 wk. Both diets were found to lower total cholesterol compared with baseline values. AE was more effective, with an 8.2% decrease (P less than 0.05) whereas AHA-III was associated with a 4.9% decrease (NS). Low-density-lipoprotein cholesterol and apolipoprotein B decreased significantly on AE but not on AHA-III (P less than 0.05). The high-density-lipoprotein (HDL) concentration did not change on AE but decreased 13.9% on AHA-III (P less than 0.01). It is concluded that AE is more effective than is AHA-III in decreasing total cholesterol, and, unlike AHA-III, it does not decrease HDL concentrations.