A study of behavior patterns in the American Goldfinch was conducted from March, 1961, through July, 1962. Observations of both caged and wild birds were integrated, and agonistic and related social behavior were discussed. An analysis of displays observed during agonistic encounters indicate that Head-up, Carpals-raised, Head-forward, supplanting, and vertical flights are associated with aggressive drives. Fluffed and crouched postures, turning the head away, or leaning away show avoidance. Displacement activities include beak-wiping, head-scratching, and "displacement breast preening." Encounters between caged birds were analyzed according to their implications with regard to aggressiveness and social hierarchy. Agonistic encounters were observed more frequently under crowded conditions and during the early portion of the breeding season than when adequate space was provided or during winter months. Males were generally more aggressive than females during the winter, with an apparent reversal at the onset of the breeding season. The social hierarchy consists of a highly unstable peck-dominance, showing many reversals and triangular relationships, but with a tendency toward male dominance in winter months, female dominance during the summer. Both sexes exhibit territoriality to a limited extent, at least at the beginning of nesting. An area of about 10 meters in diameter around the nest site is defended against other members of the species by chasing and fighting by the male, with display flights accounting for defense of an area about 30 meters in diameter surrounding the nest. The birds were found to range considerable distances from the nesting territories to forage. The female appears to be more often involved in conflicts with other species, apparently due to her increased aggressiveness during nesting combined with her isolation from other goldfinches. The author’s findings are compared with other recent studies of the behavior of fringillids.