It has been difficult to identify specific nutrients or food groups associated with breast cancer risk from epidemiological studies done in the U.S. Attention is now turning to the importance of overall eating patterns. A Greek-Mediterranean dietary pattern has great potential for cancer prevention. Two distinct aspects of this eating pattern are the type of fat consumed and a high fruit/vegetable intake relative to average intakes in the United States. We propose to develop and test an exchange list Greek-Mediterranean diet that could be used in future clinical trials of breast cancer prevention in women at increased risk. In this proposed study, women will be randomized to either continue their own usual diet or follow an intervention diet for 6 months. The intervention diet will be designed to decrease polyunsaturated (P) and saturated (S) fat intakes while increasing monounsaturated (M) fat intake. The P:S:M ratio of a typical American diet is about 1.0:1.5:1.7, and the goal for this intervention diet will be 1:2:5, which is much closer to that of the traditional Greek diet. A predominant source of fat will be olive oil. The fruit and vegetable goal will be 7-9 servings/day, depending on energy intake. These dietary changes will be achieved using individualized telephone counseling and a monthly group session with a dietitian. Menus will be provided as examples, but the diets will be self-selected. Compliance to the dietary goals will be assessed by food records and levels of plasma fatty acids, lipids and carotenoids. As a feasibility investigation for the planning of larger trials, plasma 8-isoprostane, oxidized lycopene, insulin and glucose levels will also be assessed since these may lend insight into two possible mechanisms that may be responsible for the cancer preventive effects of this diet. 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. This intervention approach can then be tested for its effects on markers of breast cancer risk in future studies.