Thirty-three cases of rheumatoid arthritis were studied, one half in therapeutic sessions: the cases were almost all women. The general psychodynamic background was a chronic, inhibited hostile aggressive state as a reaction to the earliest masochistic dependence on the mother that was carried over to the father and to all human relationships including the sexual. There were tendencies to hostility to passive husbands and masculine competition as well as masochistic serving. Anything which interfered with either trend produced exacerbation of the arthritis. The authors' formulation is that increase of dammed up aggression produces muscle spasms which may precipitate an arthritic attack. The authors recognize that these psychodynamic factors are present in many patients who do not develop arthritis and that there must be some factors in addition to increased muscle tone which contribute to the etiology of the arthritis.