Epidemiological observations indicate that a Greek-Mediterranean dietary pattern has great potential for cancer prevention, but more definitive data on the preventive effects of this diet are needed. Two distinct aspects of this eating pattern are the type of fat consumed and a high fruit/vegetable intake. If the diet is feasible, it could be used in future clinical trials of breast cancer prevention. In this study, women randomly receive either a control diet or an intervention diet for 6 months. The intervention diet replaces half of the typical American fat intake with foods such as olive oil and nuts. The fruit and vegetable goal is 7-9 servings/day and includes several categories of fruits, vegetables, and herbs. Blood samples are drawn and analyzed for fatty acids derived from fats, micronutrients from fruits and vegetables, and markers of oxidative stress. This dietary trial will provide important data on the ability of women following typical American eating patterns to change their dietary intakes to reflect a Greek-Mediterranean pattern.