The effect of blood transfusion on the postoperative recurrence of Crohn's disease has been investigated. Clinical and pathological data from 197 patients treated by right hemicolectomy between 1947 and 1988 have been analysed. Symptomatic recurrences confirmed radiologically or histologically have been recorded and cumulative recurrence rates calculated for transfused and non-transfused patients. Perioperative blood transfusion does not influence the development of recurrent disease (log rank test, chi 2 = 0.112).