The preparation of biodiesel using a scientific microwave apparatus offers a fast, easy route to this valuable biofuel with advantages of a short reaction time, a low oil/methanol ratio, and an ease of operation. The methodology allows for the reaction to be run under atmospheric conditions; it is complete in a matter of a few minutes and can be performed on batch scales up to 3 kg of oil at a time. It can be utilized with new or used vegetable oil and with methanol or ethanol with a 1:6 ratio of oil/alcohol.