A material safety data sheet or MSDS is a form containing data regarding the properties of a particular substance. It is intended to provide workers and emergency personnel with procedures for handling or working with that substance in a safe manner, and includes information such as physical data (melting point, boiling point, flash point, etc.), toxicity, health effects, first aid, reactivity, storage, disposal, protective equipment, and spill handling procedures. The exact format of an MSDS can vary from source to source.
In the U.S., OSHA requires that MSDS be available to employees for potentially harmful substances handled in the workplace under the "Employee right to know" rules.
An MSDS for a substance is not primarily intended for use by the general consumer, focusing instead on the hazards of working with the material in an occupational fashion. For example, an MSDS for a cleaning solution is not highly pertinent to someone who uses a can of the cleaner once a year, but is extremely important to someone who does this in a confined space for 40 hours a week.
External link: MSDS Search page (Cornell University), http://msds.pdc.cornell.edu/msdssrch.asp