These tables list OSHA hazard categories and Safety Data Sheet (SDS)/label information for chemicals that are in the most hazardous health and/or physical hazard classifications. OSHA hazard categories generally range from 1 to 4 with category 1 being the most hazardous. Chemicals in these categories must be judiciously evaluated prior to procuring and using them for experiments. Creating SOPs with safety information for these or including safety information in existing protocols using them is very important. References to locate lists of some hazardous chemicals are also included below.