The authors make available in this paper the text of a previously unpublished letter by Freud, probably addressed to the founder of British ecology and his former patient, Sir Arthur Tansley, F.R.S., dating from 1932, concerning the treatment and later life of ‘Anna O.’, the first psychoanalytic patient. They give the full text of Freud's letter as discovered, and offer a brief commentary on its significance as evidence of Freud's view or views of Anna O.'s treatment, case-history and later life. The authors compare the view of Anna O.'s treatment and later life with other sources, in particular Freud's roughly contemporaneous letter to Stefan Zweig. The letter's principal novel formulation is to be found in the phrase ‘a cure with a defect’, with which Freud characterised Anna O.'s experience of her treatment with Breuer.