This study analyzes various aspects of firm performance, research and development (R&D), and their relationship with firm size using Japanese and Thai firms. First, the results indicate that, to a certain degree, exporting firms of different sizes differ significantly in export performance and attitude variables analyzed. However, larger exporting firms do not necessarily perform better than smaller ones, nor do they have more positive attitudes toward exports. Second, findings show that R&D expenditure and intensity are positively related to return on assets, return on equity, gross profit margin, operating income margin, and ordinary income margin. Larger firms also proved to be more efficient in their for profit R&D management for all of the above mentioned profitability variables. Third, the results indicate that firm size is positively related with export intensity, although the relationship is positive and significant only if a firm is large, and not otherwise.