In field investigations on the relative resistance of varieties of peas, Pisum sativum L., to the pea aphid, Acyrthosiphon pisum (Harr.), the average number of aphids per terminal growth for 13 years (Maltais, 1937, 1950, 1951, and unpublished technical report, 1950-54) for six varieties was as follows: Perfection, 39.6; Daisy, 32.6; Lincoln, 35.6; Laurier (H-103), 9.8; Champion of England, 11.8; and Melting Sugar, 16.8. In a preliminary investigation by Auclair and Maltais (1950), 11 free amino acids were detected in pea plant extracts by paper chromatography. From a visual comparison of chromatograms, the variety Perfection appeared to contain a higher concentration of most free amino acids than the variety Laurier. This is a report on the quantitative estimation of the free and total amino acid contents of the three susceptible varieties (Perfection, Daisy, and Lincoln) and the three resistant varieties (Laurier, Champion of England, and Melting Sugar) by the method of paper chromatography.