The plasma membrane is the perception site for multiple signals including hormones in both plants and animals. Research done in the past decade has identified receptors and perception mechanisms of the majority of plant hormones. Molecular genetic evidence now exists for PM perception of three of the plant hormones: brassinosteroids, cytokinins and abscisic acid. It is interesting to note that three distinct PM-localized perception and signal transduction modules exist for these three hormones. Brassinosteroids are perceived by PM-localized leucine rich repeat receptor-like kinases (LRR-RLKs), cytokinins by a two-component phosphorelay module similar to the prokaryotic two-component system, and abscisic acid by an atypical G-protein coupled signaling pathway.