Background: Eustachian tube balloon dilation is a minimally invasive surgical procedure used to treat Eustachian tube dysfunction which is not responsive to conventional therapies. Methods: In this cohort intervention series we report the results of balloon dilation in treating refractory equalization problems in 20 freediving spearfishermen; in 19 cases the problem was unilateral and in one case bilateral. All the patients had already received medical and insufflation therapy and four patients had also had nasal surgery. None of these treatments or procedures had achieved improvement. We used a 20 mm x 3 mm disposable balloon catheter inserted through a 70-degree guide catheter and inflated up to 12 ATM three times at three different depths of insertion within the Eustachian tube. Every inflation lasted 120 seconds. Results: Fifteen out of 20 patients improved. Ten patients reported a complete resolution of equalization problems, five showed improvement with persistence of a slight equalization delay on the treated side. Five patients did not report any improvement. Two complications occurred: subcutaneous emphysema of the parotid region in one case; and a mild high frequency (4-8 KHz) sensorineural hearing loss in another patient. Conclusion: Balloon dilation of the Eustachian tube is an effective therapy in the treatment of equalization problems with a good success rate.