Numerous insects and other arthropods colonize and reproduce in disturbed and man-made environments. This is particularly apparent in Juban areas. The extent to which these organisms exploit urban environments has only recently been appre ciated. Our ignorance in this area can be attributed, in large part, to the general dearth of relevant ecological studies. The purpose of this review is to evaluate and synthesize information important to an understanding of the ecological bases for the reproduction and survival of insects (and to a lesser extent other arthropods) in urban environments. More specifically, we emphasize the need to assess two major components of the insect's environment: resources necessary for survival and the pervasive influence of man. Population, community, and evolutionary case-history studies are analyzed within this conceptual framework. Comparative studies in more than one habitat are given special consideration. Finally, suggestions for future studies on basic and applied questions in urban entomology are offered. Information on insects in urban environments is scattered throughout the agricul tural and biological literature. This is not surprising since most of the information has been gathered by specialists in a wide variety of fields. Examples of these fields and representative studies include: ecological and environmental sciences (56, 64, 81, 92, 117, 118, 137, 138, 159, 165, 166), population genetics and evolutionary biology (14, 17, 18,36,38-41,75,99, 151), general pest identification and control (43, 72, 150), biological and integrated control (91, 107, 108, 121, 122), forest entomology (25, 50, 51, 71, 91, 103, 130), plant pathology (53, 143), medical entomology (61, 85, 99, 124, 149, 157), stored-product entomology (10, 19,49, 70, 88, 102, 168, 174), and insecticide toxicology (16).