The authors report on the experiment carried out on the use of sodium nitroprusside (NPS) in otological surgery. The acknowledged advantages of NPS over hypotensors and more particularly its spécifically vascular, périphéral, swift action, rapidly reversible, are worth mentioning. Control over the achieved hypotension however, requires careful attention to avoid overdosage which could result in severe hypotension and "cyanhydric" intoxication. The recording of capillary pulse constitutes an easy and reliable solution to the difficulties arising from permanent control of blood-pressure and of peripheral arterial perfusion. The method both produces excellent results permitting bloodless surgery, and allows a reduction of NPS doses giver, without resorting to a invasive for measuring blood pressure. The method used in surgical fields other than otology has already proved very satisfactory.