Numerous hazardous chemicals are present in workplaces and the environment. Physicians are likely to be increasingly challenged with the evaluation of individuals exposed to these chemicals. Recent legislation mandates the creation of material safety data sheets that describe the composition and toxicity of hazardous compounds. This legislation has also greatly increased the availability of material safety data sheets to workers and physicians. While these can be of great assistance in the evaluation of exposed individuals, they often contain deficiencies that preclude the prudent physician from relying exclusively on them. A few typical material safety data sheets are reviewed to illustrate what one can expect to find.