Some microwave radiation leakage is generally associated with the operation of microwave ovens. This leakage usually occurs around the door seals and varies with the type, size, and placement of food or other loads within the oven cavity. This report describes field and laboratory studies that were performed to determine the most important variables and their effect on microwave oven radiation leakage levels. Additional field observations of ovens in use should be conducted to more clearly define the correlation between food types, sizes, and placement, and door closing and opening procedures. (Author)