BACKGROUND: Despite the frequency of intrahospital transport of critically ill patients, little research has been done on this topic and the findings are contradictory. OBJECTIVES: To describe arterial oxygen saturation by pulse oximetry, heart rate, heart rhythm, and systolic blood pressure and equipment problems in critically ill, mechanically ventilated adults during intrahospital transport. METHODS: The sample consisted of 36 critically ill, mechanically ventilated adults who required transport out of the intensive care unit for diagnostic testing or procedures within the hospital. Arterial oxygen saturation, heart rate, heart rhythm, and systolic blood pressure were measured at baseline, at least every 5 minutes during transport to and from the test site and at the test site, and every 5 minutes for 15 minutes after return to the unit. Descriptive statistics were used to analyze the data. RESULTS: Nineteen patients (53%) had clinically important changes in arterial oxygen saturation, heart rate, and/or systolic blood pressure. New cardiac arrhythmias developed in two patients. The clinically important changes occurred most frequently at the test/procedure site. Equipment problems such as monitor power failure and ventilator disconnection occurred during transport of 4 patients (11%). Total time out of ICU averaged 62 +/- 30 (range = 26 to 166) minutes. CONCLUSIONS: Transport outside the intensive care unit places the critically ill patient at additional risk. Although transport is often unavoidable, its risks versus benefits should be carefully and collaboratively evaluated for every patient prior to making the decision for transport.