The vast majority of micro and small enterprises in developing countries are located in industrial clusters, and the majority of such clusters have yet to see their growth take off. The performance of micro and small enterprise clusters is especially low in Sub-Saharan Africa. While existing studies often attribute the poor performance to factors outside firms, problems within firms are seldom scrutinized. Entrepreneurs in these clusters are unfamiliar with standard business practices. Based on a randomized experiment in Ghana, this study demonstrates that basic-level management training improves business practices and performance, although the extent of improvement varies considerably among entrepreneurs.