The last 30 years have been marked by concern regarding the effects of pesticides on human health and on the environment. Unwanted and adverse effects on man and other nontarget organisms have been reported from many countries. The health effects recorded for thousands of people yearly are mainly caused by the inappropriate handling of pesticides or by accidents. The important task is to identify and evaluate the specific hazards of the handling and application of pesticides and the need to collaborate with the World Health Organization (WHO) and other organizations on promoting the health protection of exposed workers. The selectivity of chemical control methods can often be markedly improved by the proper choice of formulation and application techniques and, of course, by an appropriate choice and use of the pesticide itself. This work is an integral part of the international program on chemical safety based on and incorporating current WHO activities. The situation in the developing countries creates a new dimension for the work to be done. In these countries the working populations are affected by the general diseases prevailing in the community, as well as by many uncontrolled hazardous agents at work.