Ten years' experience with an elemental diet in the management of Crohn's disease. The immediate and longterm outcome of treating patients with acute Crohn's disease with an elemental diet was studied retrospectively. Successful diet induced remission was achieved in 96 of 113 patients (85%) regardless of age, sex, site or severity of disease, or associated complications of strictures, fistula, or perianal disease. Treatment was unsuccessful in 17 patients (15%), but there were no features at the outset of treatment that distinguished these patients from those who had successful remission. The longterm outcome of treatment was assessed over a five year period by analysis of life tables and survival curves. Twenty two per cent of the patients relapsed within six months of treatment and thereafter the annual relapse rate was 8-10%. Patients with disease complicated by fistula or perianal involvement had early relapse, approaching 100% for the latter. A further retrospective comparison of longterm outcome of diet v steroid induced remissions showed no significant difference in the relapse rates between the two groups at one, three, and five years. 