Catheter dislodgement is a major cause of technical failures in intraarterial vasopressin therapy for gastrointestinal bleeding. Ten such cases were observed in the past five years. In seven patients catheter dislodgement led to recurrent bleeding during vasopressin infusion. In one patient aortic infusion of vasopressin caused recurrent bleeding and reversible acrocyanosis of the feet, and in two patients vasopressin infusion into the left renal artery resulted in chest pain and hematuria. Catheter dislodgement should be suspected if bleeding that was initially controlled recurs during vasopressin infusion.