Agriculture ranks among the most hazardous industries. Many new techniques and processes that are being used in agricultural production can give rise to health problems that are not readily recognized either by health professionals or the workers themselves. Agricultural workers are at high risk for fatal and nonfatal injuries, work-related lung diseases, noise-induced hearing loss, skin diseases and certain types of cancer associated with chemical use and prolonged sun exposure. Agriculture is also one of the few industries in which the families of workers, who often share the work and live on the premises, are also at risk for injuries, illness and death. This publication is intended for workers and health personnel in both industrialized and developing countries. Its purpose is to provide rural health practitioners (occupational health personnel, other health care specialists and practitioners working in parasitology, toxicology, accident prevention and primary health care) and public health officials with information related to the major problems facing agricultural workers in health practice. Fundamental principles in the development of an occupational health service are presented, with emphasis on the importance of the primary health care approach.