Background and Study Aims: Transmual endoscopic drainage of peripancreatic fluid collections under endoscopic ultrasound (EUS) control has been reported. We evaluated a facilitated technique of one-step puncture and drainage using a new stenting device and a large-channel echo endoscope. Patients and Methods: EUS-guided transumural drainage of cystic lesions was attempted in six male patients. The drainage sites were duodenal in two instances and gastric in four. The lesions were pseudocysts, arising from chronic pancreatitis (n = 2), and following acute pancreatitis (n = 3), and one abscess. The median size of the pseudocysts was 50 mm (range, 25 to 90). The punctures were carried out under direct EUS guidance, using a new echo endoscope with a 3.2-mm working channel. Transmural drainage was done using modified 7-F stents. Stents were inserted directly over a 1-mm puncture needle and their position was optimized using a 7-F pusher connected to the stent by a special construction. The stents were released by withdrawing the needle. Results: EUS-guided one-step drainage was technically successful in all 6 patients. It was possible to position the stents as desired, regardless of the location, size or pathogenesis of the target lesions. There were no complications associated with the endoscopic interventions. All the lesions, including two with putrid contents, had collapsed by the day following drainage. The stents were removed after a median period of 2 weeks (range 2 - 12). The cysts had completely resolved in four patients at follow-ups of 3 - 13 months (range). The patient with the gastric abscess underwent gastrectomy 2 weeks after stent extraction, because of a coincidental adenocarcinoma at the cardia, the abscess being resolved. One patient with necrotizing pancreatitis, who refused surgical treatment, died because of septic complications. Conclusions: New large-channel echo endoscopes allow more aggressive endoscopic interventions to be carried out safely under direct EUS control. One-step drainage using the new 7-F stent-over-needle device was effective for six cystic lesions of variable origin.