The mining regulations of all 50 states were reviewed by the Bureau of Mines, and those parts pertaining to the use of internal combustion (ic) engines (particularly diesel engines) in underground mines or confined spaces were extracted. Also extracted were subjects associated with the use of ic engines; for example, storage and handling of flammable liquids, maintenance, and ventilation requirements. As the laws now stand, 29 states have specific regulations that affect the operation of diesel engines in underground coal and/or metal and nonmetal mines. The other states have no regulations because either they have no mining activities or they defer to federal regulations. Six states have regulations expressly prohibiting the use of diesels in underground coal mines. Specific contacts (addresses and phone numbers) precede each state's regulations to facilitate inquiries about regulation revisions and interpretation.