One of the main reasons for noncompliant firms' poor environmental performance is the information gap on Mexico's environmental policy. Pollution control could be improved through systematically fuller communication targeted to noncompliant firms - including more environmental education, especially of senior managers; Survey evidence from Mexico reveals large observed differences in pollution from factories in the same industry, or the same area, or operating under the same regulatory regime. Many factories have adopted significant measures for pollution control and are in compliance with environmental regulations, but some have made little or no such effort. For lack of data, systematic research on the reasons behind such variations in plant-level environmental performance (especially on how impediments to pollution control affect plant behavior) is rare, even in industrial societies. Drawing on a recent plant-level survey of Mexican factories, Dasgupta identifies a number of performance variables characteristic of compliant and noncompliant plants, as well as factors that non-compliant plants perceive to be obstacles to pollution control. Noncompliant firms made less effort than compliant firms to change materials used, to change production processes, or to install end-of-pipe treatment equipment. They had significantly fewer programs to train their general workers in environmental responsibilities. They lagged behind in environmental training, waste management, and transportation training. They received less technical training, especially about the environment, environmental policy and administration, and clean technology and audits. Responses about obstacles to better environmental performance included scarcity of training resources, government bureaucracy, high interest rates, and Mexico's lack of an environmental protection culture. Respondents said that senior managers did not emphasize the environment, assigned more priority to economic considerations, and were not trained in the subject. There were too few suitable programs, training was not recognized, and workers were not interested in the subject. Most important, however, little information was available about Mexico's environmental policy. These findings suggest the importance of technical assistance - especially training and information. In Mexico, the information gap on policy is a major problem. Mexican environmental agencies should invest more in technical assistance and environmental training targeted to noncompliant enterprises. Environmental education, especially of senior managers, could significantly improve pollution control. Maintaining close contact with noncompliant firms, designing programs targeted to them, and pursuing them systemically should increase their responsiveness to regulations. This paper - a product of Infrastructure and Environment, Development Research Group - is part of a larger effort in the group to understand the determinants of environmental performance in developing countries. The study was funded by the Bank's Research Support Budget under the research project The Economics of Industrial Pollution Control in Developing Countries (RPO 680-20). The author may be contacted at sdasgupta@worldbank.org.