In spite of the outstanding successes achieved in the control of arthropod vectors with insecticides, serious difficulties have been encountered in recent years. This has led to renewed interest in the possibilities of biological and other methods of control. The author reviews briefly relevant aspects of the biology of vectors, with examples from various groups. A thorough knowledge of the ecology of the vectors and their breeding habits may sometimes permit control by manipulation of the environment, by attacking animal reservoirs of disease, or by the introduction of predators, pathogens or parasites. The injudicious use of these methods may, however, upset the biological balance and recoil dangerously. Answers to the problems involved will be found more readily if specialists can arrange to pay frequent visits to the field and undertake field work themselves. There is also a need for closer co-operation among workers in different scientific disciplines; this would enable the various approaches to be co-ordinated and promote the achievement of integrated control.