A 19-year-old woman with a known allergy to iodinated contrast presented with intermittent, gross hematuria of 2 years' duration. The patient was scheduled to undergo cystoscopy with bilateral retrograde pyelography, because this is considered a safe alternative to intravenous pyelography or computed tomography. Because of her contrast allergy, the patient completed a 13-hour steroid preparation before the procedure. However, within minutes of extubation, she developed an anaphylactoid reaction and, despite appropriate management, required reintubation and subsequent transfer to the intensive care unit. The patient was subsequently extubated 8 hours later and recovered completely.