Hyponatremia, caused by absorption of hypotonic irrigating fluids, is a well-documented complication of surgical procedures such as transurethral resection of the prostate (TURP). Although not commonly mentioned in the renal literature, there have been several case reports of hyponatremia associated with hysteroscopic endometrial ablation that also were considered to be attributable to absorption of hypotonic fluid. We present a 43-year-old white woman who underwent endometrial ablation for menorrhagia under general anesthesia. Postoperative serum chemistries showed a sodium of 112 mEq/L and an osmolality of 234 mOsm/L, and urine chemistries showed a sodium of 125 mEq/L and an osmolality of 629 mOsm/L. Although fluid retention of hypotonic irrigating fluid clearly contributed to the hyponatremia, search for associated morbidity showed an absence of either osmotic or volume stimulus to account for the apparent antidiuretic effect, suggesting the participation of a postsurgical, stress-related ADH release. We conclude that hyponatremia associated with hysteroscopic endometrial ablation may be multifactorial.