Elevated serum cholesterol levels play an important role in the development of coronary artery disease. Previous studies have suggested that nut consumption benefits lipid profile. Pistachio nuts are widely available, inexpensive and frequently consumed by the general population. To determine whether substituting 20% of the daily caloric intake in the form of pistachio nuts will improve the lipid profiles of humans with primary, moderate hypercholesterolemia. Controlled, randomized crossover design. Outpatient dietary modification, counseling and blood analysis. Ten patients with moderate hypercholesterolemia. Three weeks of dietary modification with 20% caloric intake from pistachio nuts. Body weight, blood pressure, total cholesterol, LDL, HDL, and triglycerides were monitored. Lipid profiles were analyzed prior to, during and after dietary modification. After three weeks, there was a decrease in total cholesterol (p<0.04), an increase in HDL (p<0.09), a decrease in the total cholesterol/HDL ratio (p<0.01) and a decrease in the LDL/HDL ratio (p<0.02). Triglycerides and LDL levels decreased, but not significantly. Body weight and blood pressure remained constant throughout the study. Results suggest that eating pistachio nuts instead of other dietary fat calories can improve lipid profiles, thereby decreasing coronary risk. Further studies will be required to confirm these results and to determine the mechanism of this effect.