Aim: We aimed to compare patients who developed complications during endotra-cheal intubation and who did not develop any complication in the Medical Intensive Care Unit. Material and Methods: We enrolled 39 patients into the study. Patients intubated outside the intensive care unit (emergency service, prior to operation) were excluded. All intubation procedures were performed by residents in internal medicine. Data about the patient and complications were recorded by the same person. Results: At least one complication was seen in 41% of all patients. Life-threatening complications such as severe hypoxemia (12%) and severe cardiovascular collapse (7%) were found. Diffcult intubation (23%), aspiration (10%), esophageal intubation (10%), dental injury (10%), and dangerous agitation (3%) were found as moderate complications. Acute respiratory failure was the most common reason for intensive care unit admission (59%) and intubation (74%). Within one hour before intubation, the highest and lowest mean heart rate was higher than those who developed complications. No complications were observed in patients who were intubed at the frst attempt. All complications occurred in patients who had two or more trials. Conclusion: Complications of endotracheal intubation is an important problem in intensive care units. Intubation success on the frst attempt prevents complications. As the number of endotracheal intubation with the assistance of laryngoscopy increased, it was seen that complications related to the procedure also increased.