Obesity has been described as a relative contraindication for percutaneous tracheostomy. The objective of our study was to examine the safety and complications of percutaneous tracheostomy in obese patients. We conducted a prospective cohort study of all consecutive patients who underwent percutaneous tracheostomy at a tertiary medical-surgical intensive care unit between May 2004 and October 2005. We compared percutaneous tracheostomy in obese patients (body mass index > or = 30 kg/m2) to non-obese patients. We documented the occurrence of the following complications: aborting the procedure, accidental extubation, conversion to surgical tracheostomy, paratracheal placement, the development of pneumothorax, major bleeding (requiring blood product transfusion or surgical intervention) or death. We also documented hypoxia, minor bleeding (requiring pressure dressing or suturing), subcutaneous emphysema and transient hypotension. During the study period, 227 percutaneous tracheostomies were performed. There were 50 percutaneous tracheostomies in the obese group and 177 in the non-obese group. In 45 obese patients, percutaneous tracheostomy was performed without bronchoscopic guidance. Major complications were significantly higher in obese patients (12% vs. 2%, P = 0.04), while the rate of minor complications was not significantly different between the two groups. There were no instances of death or pneumothorax, subcutaneous emphysema or need for surgical intervention during or in the postoperative period in either group. Our study suggests that percutaneous tracheostomy can be performed safely in the majority of obese patients.