A dynamic framework based on the process of firm selection and industry evolution is used to analyse the post-entry performance of new firms. In particular, it is hypothesized that, based on the stylized fact that virtually all new firms start at a very small scale of output, firm growth and survival are shaped by the need to attain an efficient level of output. The post-entry performance of more than 11,000 U.S. manufacturing firms established in 1976 is tracked throughout the subsequent tenyear period. Firm growth is found to be negatively influenced by firm size but positively related to the extent of scale economies, capital intensity, innovative activity, and market growth. By contrast, the likelihood of survival is identified as being positively influenced by firm size, market growth, and capital intensity, but negatively affected by the degree of scale economies in the industry. When viewed through the dynamic framework of firm selection and industry evolution, the empirical results shed considerable light on several paradoxes in the industrial organization literature, such as the continued persistence over time of an asymmetrical firm-size distribution consisting predominantely of suboptimal scale firms, and the failure of capital intensity and scale economies to substantially deter the entry and start-up of new firms.