Several microwave double-resonance experiments using high pumping power have been carried out in ethylene oxide molecules. The characteristics of the double resonance, such as the splitting or the "pulling" of the signal, have been observed magnified by the use of high power. The M fine structure of the signal has been observed for the first time. By the use of collision-induced transitions, the formula of Karplus and Schwinger for saturation has been confirmed at the high-power level. Applications of the technique for additional studies of molecular problems are discussed.