There have been rapid advances in elucidating the mechanisms of ethylene perception and synthesis by plants, the signal transduction pathway, and ethylene control in transgenic plants. It is noted here that studies on ethylene have led the way in enhancing our understanding of the biosynthesis of a plant hormone at the biochemical and molecular levels, and future studies should further help in the understanding of the biochemical machinery responsible for the perception and signal transduction of this plant hormone. The purpose of the papers here is the critical assessment of the ethylene synthesis, perception and signal transduction, its role in pathogenesis and stress, its involvement in plant growth and development and, lastly, the biotechnological control of its formation and function.