The authors describe their experience in treating 72 patients with pneumothorax by placement of a drainage tube of 2.2 mm internal diameter equipped with a Heimlich valve. Full lung expansion was achieved with this method in 93% of the cases. Mean hospital stay was 4.05 days (Sx = 3.4, minimum 1, maximum 20). In 7 (10.7%) cases out of 64 who were discharged and followed as outpatients, there was recurrence of pneumothorax. With these results the authors conclude that the system used is valid for treating pneumothorax and that large drains and water seals are not necessary in most cases.