Using Allen's test, impaired ulnar artery circulation to one or both hands was detected pre-operatively in five out of ten acromegalic patients scheduled for transphenoidal hypophysectomy. Three of these patients also had symptoms of compression of the median nerve at the wrist (carpal tunnel syndrome). If ulnar flow is considered to be inadequate cannulation of a dorsalis pedis artery provides one possible alternative route for continuous measurement of the blood pressure during induced hypotension. In the three patients in this report in whom this vessel was cannulated no ischaemic complications in the foot were seen.