The concept of using alcohol fuels as alternatives to diesel fuel in diesel engines is a recent one. The scarcity of transportation petroleum fuels which developed in the early 1970's spurred many efforts to find alternatives. Alcohols were quickly recognized as prime candidates to displace or replace high octane petroleum fuels. However, alternatives to the large demand for diesel fuel in many countries were not as evident. Innovative thinking led to various techniques by which alcohol fuels can partially or completely displace diesel fuel in diesel transportation vehicles.The methods of using alcohol fuels in diesel engines (in order of increasing diesel fuel displacement) include solutions, emulsions, fumigation, dual injection, spark ignition, and ignition improvers. Power output, thermal efficiency and exhaust emissions can change significantly depending on the techniques employed. Reliability and durability still need to be demonstrated for most of these techniques.Work in the future will determine which of these techniques are best. Testing will evolve to include more on-road, in-use type tests. Additional techniques such as “hot-spot” ignition will be researched.