An efficient method was developed for the synthesis of 3,4,5-trisubstituted and 3,5-disubstituted isoxazoles by using con-tinuous-flow microwave-heated microreactors. A study on the sep-arate effects of the temperature, continuous-flow regime, and microwave irradiation showed that the continuous-flow regime had important effects for less reactive diketones, where microwave heating enhanced the reaction, permitting the formation of 5-meth-yl-3-phenylisoxazole, which was not formed in the absence of mi-crowaves.