Market efficiency and buyers' risk strategy in the Japanese coking coal import market are examined. The Japanese coal market is found to be inefficient, Japanese buyers traditionally have purchased coals from the United States at a high price and, since the second half of the 1980's, have paid the highest average price to Canadian producers. Given the abundant low cost Australian coals, this purchasing pattern does not meet the cost minimization criteria for efficiency. This is explained mainly by the buyers' risk management strategy. To more accurately examine price differentiation, the complexity of coal quality is considered first. A statistical method is used to estimate the quality premium as a cost component in price formation. Next a comparison of supply regions and a detailed investigation on market conduct is based on quality-adjusted prices, which are assumed to represent the prices of homogenous coals. Although various reasons are used by researchers to explain Japanese buyers power, this study finds vertical integration of the Japanese companies to be the most important factor creating that power. A detailed survey of vertical integration is made. Finally, a monetary value of the risk premium is estimated by using the partial elasticity of substitution. Total payments by Japanese coking coal buyers for risk premiums are estimated. These represent the extra dollars paid by the Japanese to US and Canadian coal producers for purchasing their coals instead of Australian coals.