Application of pesticides in agriculture is still the most effective and accepted means for production of better crops. Their widespread application shows deleterious effects on the environment and human life in different ways. It is usually connected with serious problems of pollution and health hazards [1-7]. A subtle danger from wide scale use of these chemicals may be mutagenesis and toxicity to a broad range of organisms, either by direct exposure or by their ingestion through the food chain [8-11]. Whereas several studies have reported adverse effects of pesticides on chromosomes in a laboratory test system [9,12-17], few have been done in populations occupationally exposed to pesticides [18,19]. In studies of chromosome aberrations in workers occupationally exposed to pesticides both positive [3,18-21] and negative findings [22,23] have been reported. This prompted one to study the cytogenetic effects in agricultural workers occupationally exposed to pesticides in Jordan, most of whom are not protected during their use in the fields.