The three main purposes of this paper are to (1) identify critical success factors(CSFs) for electronic commerce(EC), (2) investigate the explanatory power of these CSFs on firm performance, and (3) compare differences in evaluating CSFs and explaining impact of CSFs on performance among Korea, Japan, and U.S.A. EC firms. Through a literature review and interviews with managers in EC firms, a list of 16 CSFs consisting of 111 items was compiled. In the second stage, questionnaires were administered to managers of EC companies in Seoul, Korea, Tokyo, Japan, and Texas, U.S.A. Survey results show that CSFs have very significant explanatory power for firm performance in Korea, Japan, and U.S.A. While security, privacy, technical expertise, information about goods/services, and variety of goods/services are the most explanatory CSFs in Korea and Japan, evaluation of EC operations, technical expertise, and ease of use show most explanatory power in U.S.A. In general, respondents in Korean and Japan evaluate CSFs quite differently compared to U.S.A counterparts.