To examine the effects of avocado on plasma lipid concentrations, a three-diet trial involving 16 healthy volunteers was carried out. A diet rich in monounsaturated fatty acids using avocado as their major source (30% of the total energy was consumed as fat: 75% of the total fat from the avocado), with restriction of saturated fats and less than 300 mg of cholesterol per day was evaluated. Subjects also were in a free-diet period with the addition of the same amount of avocado. Finally, volunteers received a low-saturated fat diet without avocado. The first and third diets were designed to simulate a usual diet and volunteers carried on their normal activities during the trial, only the three daily meals were eaten in our clinical unit. Diets lasted 2 weeks and they were assigned in a randomized order. In both rich-monounsaturated fat (RMF) and low-saturated fat (LSF) diets, there were similar reductions in the plasma total cholesterol and low-density lipoprotein cholesterol levels. The levels of high-density lipoprotein cholesterol significantly decreased (p < 0.05) after 2 weeks of the LSF and free monounsaturated-enriched (FME) diets. The plasma triacyglycerol levels lessened after RMF and FME diets, while LSF diet increased them. In total cholesterol and in low-lipoprotein cholesterol levels, there were statistically significant differences between the FME and the LSF diet periods. Avocado is an excellent source of monounsaturated fatty acid in diets designed to avoid hyperlipidemia without the undesirable effects of low-saturated fat diets on HDL-cholesterol and triacylglycerol concentrations.