The advantages of improved efficiency of oxygen delivery-enhanced patient compliance and improved patient functional status-recommend transtracheal oxygen therapy over oxygen delivery by nasal cannulae. However, complications of transtracheal oxygen therapy also have been described. We report our initial experience with 21 patients undergoing transtracheal oxygen therapy (TTOT) at the Cleveland Clinic between October 1986 and June 1988. Overall, a total of 120 adverse events grouped into 25 types and 4 general categories are noted. On average, each patient experienced 5.7 complications or 0.7 complications per patient-month. Overall, few complications were severe enough to discourage continued use of TTOT; only 4 patients discontinued TTOT as a result of problems they encountered. No deaths resulted from TTOT, although a few serious and potentially serious complications occurred. These included acute respiratory failure, misplacement of catheters into the middle and anterior mediastinum, and moderate hemoptysis. Most other complications were minor and resolved with time or with conservative management. Practitioner awareness of potential complications will facilitate TTOT candidate selection and the anticipation of postprocedure care problems.