Objective: Pheochromocytomas are rare chromaffin cell-derived tumors causing paroxysmal episodes of headache, palpitation, sweating and hypertension. Life-threatening complications have been described in case reports and small series. Systematic analyses are not available. We took an opportunity of a large series to make a survey. Design and methods: We analyzed records of patients diagnosed with pheochromocytomas in three geographically spread German referral centers between 2003 and 2012 (nZ135). Results: Eleven percent of the patients (ten women, five men) required in-hospital treatment on intensive care units (ICUs) due to complications caused by unsuspected pheochromocytomas. The main reasons for ICU admission were acute catecholamine induced Tako-Tsubo cardiomyopathy (nZ4), myocardial infarction (nZ2), acute pulmonary edema (nZ2), cerebrovascular stroke (nZ2), ischemic ileus (nZ1), acute renal failure (nZ2), and multi organ failure (nZ1). One patient required extracorporeal membrane oxygenation due to a hypertensive crisis with lung edema occurring during delivery (nZ1). Two patients died of refractory shock and pheochromocytomas were found postmortem. Two patients were treated by emergency surgery. Compared to pheochromocytoma patients without life-threatening events (nZ120), patients with complications had a significant larger maximal tumor diameter (7.0 vs 4.5 cm, P!0.01), higher levels of catecholamines (20-vs ninefold upper limit of normal, P!0.01), and tended to be younger (42 vs 51 years, PZ0.05). Conclusion: Although pheochromocytomas are rare, they are likely to be associated with a life-threatening situation. Clinicians have to be aware of these situations and perform a timely diagnosis.