Introduction: Biodiesel is an alternative to petroleum diesel. Biodiesel is permanently thinned plant- or animal-based oil, with a viscosity approximating that of standard No.2 diesel fuel. The fuel is called biodiesel because it is made from mostly biodegradable materials and can be used as fuel in diesel engines. Biodiesel can also be used in boilers or furnaces designed to use heating oils or in oil-fuelled lighting equipment. It can be used neat, meaning 100-percent biodiesel, or it can be blended with petroleum diesel. The purpose of this publication is to describe how people can make biodiesel to provide fuel for diesel machinery on a farm or ranch. Please note that biodiesel used on public roads is subject to federal, state and local taxes, just as petroleum diesel is. Biodiesel can be made in any quantity, from 1cup to many gallons. The process described here is a batch process, which is appropriate for an individual farmer or rancher. Steady flow processes are more appropriate for biodiesel manufacturing plants. Because small mistakes are preferable to large mistakes, people interested in making biodiesel may want to start with small batches and work up to making larger batches.