In addition to the chemical, physical, flammability, thermal, electrical and radiation hazards common to laboratories in general, toxicology laboratories have specific occupational hazards that require their recognition, appreciation and development of management practices for protective and precautionary measures. These include exposure to test chemicals of poorly understood toxicology and to control chemicals of high biological potency. Additionally there may be exposure to allergenic materials such as latex or animal allergens, and to transmissible animal diseases. This chapter reviews the routes and natures of hazardous exposures in the toxicology laboratory, specific allergenic and infective problem areas, and necessary protective and precautionary measures.