The pea aphid, Acyrthosiphon pisum (Harris), feeds mostly on leguminous host plants, including peas and alfalfa. Aphid salivary secretions may be a key element in understanding insect-plant interactions. Salivary proteins may perform multiple functions, including digestion, lubrication of mouth parts such as stylets, detoxification, excretion, defense against predators, pH regulation, and suppression of host defenses or elicitation of host responses. Salivary proteins directly interact with plant tissues perhaps eliciting responses which may benefit the insect. In an effort to isolate and identify key components in salivary secretions, we created a salivary gland cDNA library. Several hundred randomly selected cDNA clones were sequenced. Using tBLASTx, we grouped these sequences into 285 sets or clusters of essentially identical sequences. About 40% of the clusters matched clearly to proteins of known function in other species. Of these, 81% had their top matches to an insect protein. In this paper, we report cloning of a highly abundant cDNA from the cDNA library of salivary glands of pea aphid. cDNA encodes for a novel gene that fails to match to a protein of a known function. cDNA encodes for a 21.8 KDa protein with a secretion signal, indicating that it is a secreted protein in the saliva and may play an important role in aphid-plant interactions.