Percutaneous catheter drainage (PCD) of pancreatic pseudocyst has been reported to have good therapeutic results. low complications, and short hospital course. To find the clinical and radiological findings which can predict the treatment period for PCD, we retrospectively correlated the clinical data (presence of invection, initial and 1 week follow-up seruma and aspirate amylase level, daily drainage amount) and radiological findings (evidence of fistula, PCD route, inital size of pseudocyst) with the treatment period in each case, The age ranged from 20 to 64 years (mean :39.8 years)and male to female ratio was nine to one. When the cavity was obliterated after PCD and did not recur after tube removal without a surgical treatment, we regarded the patient to be cured. Mean treatment period was 20.2 days and nine patients (90%) were cured. We think that the factors shortening treatment period are the presence of superimposed infection and the abrupt decrease of the amount of daily drainage for the first week. But the presence of fistula to the pancreatic duct may prolong the treatment period. In conclusion, PCD is safe and effective in the treatment of pancreatic pseudocyst, and the clinicla and radiological findings are expected to be able to predict the treatment period of PCD.