This dissertation is a collection of three separate but related papers which are devoted to the empirical studies of Taiwan's CPA service industry based on the 1994 survey data. The first paper applies the Zeilner's seemingly unrelated regression technique to a simultaneous system of a translog multi-product cost function and its corresponding factor share equations to investigate the extents of economies of scale and scope in Taiwan's CPA service industry. The empirical results show that product-specific scale economies exist for auditing, tax and management advisory services; ray scale economies are significantly present; and economies of scope do significantly exist in providing tax and management advisory services. The second paper uses DEA to assess technical efficiency of CPA firms, and applies the Tobit censored regression model to examine the relationship between technical efficiency and firm-specific attributes. The results show that CPA firms in Taiwan could have reduced inputs by 27.8 percent, on average, and still have produced the same level of services; a firm's size, age, service concentration and CPA-to-employee ratio have positive impacts on its technical efficiency; the firms with branches are less technically efficient than those without any branch; and the training expenditure per employee of a firm is positively related to its technical efficiency. The third paper uses DEA to assess cost efficiency, technical efficiency, allocative efficiency, as well as scale efficiency of CPA firms, and further applies the multiple regression analysis to investigate the relationship between the firm's profitability and these efficiency measures. The results show that despite the differences in mean technical and cost efficiency measures across two output specifications, CPA firms generally suffer more from technical inefficiency than from allocative inefficiency; cost efficiency measures, or their decomposed parts, technical and allocative efficiency measures, as well as scale efficiency measures all have positive impacts on CPA firms' profitability and each efficiency measure plays an important role, especially when outputs are measured in terms of revenues, in explaining the variations in profitability across CPA firms.