US market share of the Japanese soybean market declined from 91 percent in 1970 to a record low of 75 percent in 1989. In the Japanese market US soybeans compete against Brazilian soybeans. Brazilian soybean exports have increased as soybean production has expanded. Though US soybeans remained price competitive throughout the 1970-1989 study period, both volume and market share of US soybeans have decreased since 1985. The loss of market share indicates loss of competitive position. The demand for soybeans in the import dependent Japanese market is derived from the demand for the oilseed processed products of vegetable oil and protein meal. Through the Japanese tariff structure which taxes vegetable oil imports from countries outside the Pacific Rim and a private sector Japan/China barter agreement under which soy meal is imported from China, the relative demand for Japanese processed oilseed products has been influenced. Historically, US soybeans had lower levels of oil, and protein compared to Brazilian soybeans. A programming model of Japan feed-use oilseeds and oilseed processed products, vegetable oil and protein meal is developed to analyze non-price and price factors of competition for US soybean imports. / Master of Science