Conventional insecticides of broad spectrum have been widely used as the main tools for controlling insect pests. However, as the consequence of their toxicity and deep environmental impact, new biorational, and more specific approaches have been developed. In this review we present an overview of those pest control approaches which have resulted from studies dealing with inhibition of the enzymes involved in the physiology, growth, molting, development and reproduction of insect pests. These approaches involve synthetic compounds from laboratory studies and natural chemicals present in the crop plants. Recent developments using inhibitors expressed in transgenic plants are also outlined.