The trigemino-cardiac reflex (TCR) is a well-known reflexive response in which bradycardia, hypotension, and gastric hypermotility are induced by stimulation of a peripheral or central portion of the trigeminal nerve. This reflex occurs during craniofacial surgery and other operations on or near the cerebellopontine angle, petrosal sinus, orbit and trigeminal ganglion. TCR is a well-known, although not well documented, phenomenon commonly observed during trans-sphenoidal surgery for resection of pituitary adenomas. We report a case in which asystole occurred during trans-sphenoidal surgery on a pituitary adenoma that was infiltrating the right cavernous sinus. When the anesthesiologist reported asystole, the team stopped manipulation and administered intravenous atropine. Intra-operative MRI showed a small tumour remnant in the right cavernous sinus. The operation was terminated but subsequent radiosurgery was planned for the residual tumor. Although TCR is rare and usually self-limiting, this case led us to change our treatment strategy. Surgeons who perform trans-sphenoidal surgery should be aware of this potential problem. Invasive pituitary adenomas should be removed gently and the risk of triggering TCR should be kept in mind. (C) 2008 Elsevier Ltd. All rights reserved.