We report two cases of TURP (transurethral resection of prostate) syndrome showing severe cardiovascular depression without any neurological disturbances. One patient developed hypotension (62/42 mmHg) and ST segment depression (-2.7 mm) on ECG during TURP. Another patient developed hypotension (60/38 mmHg) and nodal bradycardia (34.min-1) 15 minutes after the operation. No neurological signs were observed, despite severe hyponatremia (113 and 117 mEq.l-1, respectively). It is highly likely that hypovolemia and/or electrophysiological inhibition of pacemaker cell due to hyponatremia caused the symptoms. We emphasize that sudden circulatory depression as well as neurological disorders should be recognized as a major symptom of TURP syndrome.