The cases of seven adults who ingested jack o'lantern mushrooms are presented. All patients experienced nausea and vomiting associated with abdominal cramping, and three reported diarrhea. Four of the seven complained of weakness and dizziness. Two were diaphoretic on physical examination. All seven were given IV fluids and oral activated charcoal in a local emergency department and admitted overnight for observation. Laboratory studies showed three of the seven patients to have mildly elevated liver function tests. One patient had hypokalemia requiring potassium supplementation. All were discharged the following day with normal follow-up examinations and laboratory studies. We recommend that all patients presenting with jack o'lantern mushroom poisoning be observed and rehydrated and have baseline liver function tests and potassium levels obtained.