The principles of occupational health may be the same in the developed and developing countries. However, there can be a wide diversity in practice. The exposure to chemicals at the workplace in developing countries is usually of a different nature, and the level of exposure is generally of a higher magnitude. The leading occupational diseases in developing countries are also very different to those reported in industrialized nations. For hazard evaluation in developing countries, more factors need to be considered. Problems are usually more complicated as most workplaces are subjected to many factors which typify small-scale industries. Low capital investment often culminates in cutbacks on necessary expenses, especially on occupational or environmental health activities. Thus the health, safety, and welfare of the workers are usually overlooked. This situation helps only to promote greater risks to the workers. Furthermore, many workers in the developing countries suffer from poor nutrition, endemic diseases, and other debilitating conditions. For these reasons, it is possible that currently recommended occupational exposure limits could allow injury to workers in the developing nations. When carrying out health assessment, careful attention must be paid to cultural practices, genetic components, working conditions, and other predisposing factors. This paper reviews some of the current techniques commonly used for the monitoring of toxic substances and an in-depth discussion on various problems facing the developing countries concerning the usage of these techniques.