Highly sensitive and specific recognition systems for microbial pathogens are essential for disease resistance in plants. Structurally diverse elicitors from various pathogens have been identified and shown to trigger plant defense mechanisms. Elicitor recognition by the plant is assumed to be mediated by receptors. Plant receptors for fungus-derived elicitors appear to reside preferentially in the plasma membrane, whereas viral and bacterial elicitors may enter the plant cell and are perceived intracellularly. Receptor activation initiates an intracellular signal transduction cascade leading to stimulation of a characteristic set of plant defense responses. Isolation of plant elicitor receptors and their encoding genes is expected to provide significant information on the molecular basis of signal perception and intracellular signal generation in plant-pathogen interactions.