The study attempts to investigate the relationship between inventory management and firm performance using a multi-dimensional aspect of inventory management with respect to lean management practices across countries. Research design, data, and methodology - 1643 manufacturing firms from Japan and the US that SIC ranges from 2000 to 3999 were chosen to conduct the empirical test. This study employs hierarchical OLS regression analysis to examine the impact of control variables, ABI, EBI, and the interaction between ABI and EBI on firm performance. Results - The result indicates that in Japan high level of inventory negatively influences the accounting flows of business, while US manufactures exhibit strong positive impact of ELI on firm performance across accounting and market measures. The results show that the complementarity between the amount and the speed of inventory does exist. Except for Tobin’s q, the sign of interaction term coefficient is negative, suggesting that when the amount of inventory increases and it stays longer in a firm, market values, ROS, and ROA suffers. Conclusions - The major finding of this study is that there exist some complementarities between the scope and implication of inventory management for lean strategy across countries, particularly in U.S. and Japanese firms.