The main objective of this work was to investigate the C18 fatty acids esterification under microwave irradiation. The effects of alcohol used (methanol or ethanol), temperature (150-225 degrees C), molar ratio of alcohol/fatty acid (3.5-20), and total microwave irradiation power on the noncatalytic reaction conversion were evaluated. The results showed conversion up to 60% in 60 min of reaction. The temperature presented a pronounced effect on the conversion, following an exponential dependence. The results for a distinct molar ratio of alcohol/fatty acid indicated that the increase of this parameter lead to a decrease on the reaction conversion. In general, the esterification reaction under microwave irradiation yielded similar results to those obtained with the conventional heating but with very fast heating rates.