Ultrasonography is a widely used imaging technique whose popularity is based, in part, on its reputation for being relatively without risk to the patient. Like most procedures, however, ultrasound studies may be associated with complications, as the case presented here illustrates. A 79-year-old woman was given a large oral water load before a pelvic ultrasound examination and experienced symptoms of acute water intoxication afterward. When hyponatremia was corrected, the patient's condition returned to normal.