To evaluate the effect of prostaglandin E1 (PGE1) induced hypotension on spinal blood flow (SBF) during spinal surgery, SBF was measured under isoflurane anaesthesia by the heat clearance method in 10 patients with spinal tumour. An initial dose of 0.1 microgram/kg/min of PGE1 was administered intravenously after spinal opening and the dose was adjusted to maintain the mean arterial blood pressure (MAP) at about 60 mmHg. PGE1 was discontinued at the completion of the operative produces. After starting PGE1, MAP and rate pressure product (RPP) decreased significantly compared with preinfusion values (P < 0.01), and the hypotensive effect of PGE1 remained constant at 60 min after its discontinuation. Heart rate (HR) did not change throughout the study. SBF showed no change over the course of PGE1 induced hypotension (preinfusion: 47.8 +/- 21.7 ml/100 g/min, at 15 min: 41.2 +/- 16.9 ml/100 g/min, at 30 min: 40.4 +/- 16.8 ml/100 g/min, and at 60 min: 46.1 +/- 16.3 ml/100 g/min, respectively). These results suggest that PGE1 may be a useful drug for hypotensive anaesthesia in surgery for spinal cord tumours because PGE1 maintained SBF.