23 consecutive patients (13 women, 10 men; mean age 31 years) with acute exacerbation of Crohn's disease were treated by a dietary regimen based on "resting" the bowel by parenteral nutrition or a balanced synthetic diet (Vivasorb), followed by stepwide introduction of a low-residue diet. Cardinal symptoms such as severe abdominal pain, diarrhoea, incomplete ileus or weight loss responded favourably to treatment in each case. Postoperative fistulae closed in two of three patients. Enterocutaneous fistulae, however, remained open in all five patients, although the volume of secretion decreased distinctly in four. During the follow-up period (averaging nine months after discharge from hospital) symptoms recurred in five patients, necessitating operative treatment in three.