It has been more than a centaury since the identification of ethylene as a gaseous plant hormone, and the effects of ethylene on plants have enabled broad applications in agriculture. Efforts had been made to understand ethylene signal transduction in plants, but it had not been successful until the identification and cloning of the first plant hormone receptor gene, ETR1, in Arabidopsis a decade ago. Comprehensive genetic studies allow the dissecting of the signaling pathway to reveal the components involved, which makes the studies of ethylene signal transduction become one the most-understood signal transduction pathways in plants. The identification of the signaling components and the genetic model of ethylene signal transduction pathway are described in this review.