Exosomes are extracellular vesicles (EVs) that play a central role in intercellular signaling in mammals by transporting proteins and small RNAs. Plants are also known to produce EVs, particularly in response to pathogen infection. The contents of plant EVs have not been analyzed, however, and their function is unknown. Recent work in the Innes laboratory has revealed that plant EVs are highly enriched in proteins involved in biotic and abiotic stress responses, and carry miRNAs. In addition, EV secretion is enhanced in plants infected with Pseudomonas syringae and in response to treatment with salicylic acid. These findings suggest that EVs represent an important component of the plant immune system. In this talk I will present our ongoing investigations into the possible functions of EVs, and our initial investigations into the genetic requirements for EV biosynthesis.