Some microrganisms have evolved to be associated with plants, receiving nutrients from plants, and helping plants to fight pathogens by producing microbial elicitors, which are compounds that trigger plant defenses. Elicitors are thus safe compounds that can replace harmful pesticides for a sustainable agriculture. Here we review plant immunity and microbial elicitors with focus on antibiotics, volatile organic compounds, siderophores, antimicrobials, enzymes, salicylic acid, methyl salicylate, benzoic acid, benzothiadiazole and chitosan.