OBJECTIVE: To evaluate the safety of the balloon occlusion test(BOT) and therapeutic occlusion of the internal carotid artery(ICA). METHODS: The data of 43 patients hospitalized consecutively with traumatic intractable carotid cavernous fistulas (TICCF) were analyzed. Therapeutic occlusion of ICA was performed on 39 cases and BOT was only performed on the remaining 4 cases. Our assessment consisted of: (1) angiographic evaluation of collateral circulation with or without BOT of ICA, and (2) evaluation of clinical tolerance to therapeutic occlusion of ICA with hypotensive challenge for 30 minutes. Complications of BOT and therapeutic occlusion of ICA were also analyzed retrospectively. RESULTS: Complications related to BOT occurred in 1 case (2.3%) without causing permanent deficits. Complications related to therapeutic occlusion of ICA occurred in 4 cases (10%), including 1 technical (2.5%), 2 temporary (5%) and 1 permanent (2.5%) deficit. There was no fistula recurrence or mortality. CONCLUSIONS: BOT of ICA is safe and economical. The reliability of the results is almost the same compared with that of other more complicated methods of assessing therapeutic occlusion of ICA. And it is easy to treat TICCF with therapeutic occlusion of ICA.