Peanut (Arachis hypogaea L.) cultivars (Starr and Florunner) and four peanut introductions (PI 261945, 261946, 261973, and 261980) were each separately inoculated with a mild strain (M2) and with the necrosis strain (N) of peanut mottle virus. The effects of these viral strains on the chemical composition of peanut seed were evaluated. The chemical characteristics varied with the type of viral infection. The greatest effect was on fatty acids and the least on the total amino acids. In general, peanuts infected with the necrosis strain showed: (1) a decrease in the percentages of stearic and oleic acids, while linoleic, arachidic, behenic, and lignoceric acids increased, (2) increases in the levels of the free amino acids glycine, alanine, isoleucine, histidine, lysine, and arginine, and (3) the total amino acids exhibited a slight decrease in aspartic acid and a slight increase in methionine. Peanuts infected with the mild strain generallly showed: (1) a slight increase in linoleic acid, (2) little effect on the free amino acids, and (3) a small increase in tyrosine and a slight decrease in serine and aspartic acid for the total amino acids. No treatment effect was noted on protein content.