Small-bore percutaneous drainage catheters have been used extensively in the management of abdominal disorders and are gaining acceptance in thoracic problems. The records have been reviewed in 44 consecutive patients in whom 53 small-bore catheters were placed for thoracic disease, including empyema, 20; effusion, 9; pneumothorax, 10; lung abscess, 4; and mediastinal cyst, 1. Insertion was performed under fluoroscopy in 88%, computed tomography in 6%, and ultrasonography in 6%. Catheters ranged in size from 6.5F to 12F, but catheter size did not seem to influence outcome (p = 0.6). There was complete resolution of the problem in 75% (33 of 44) of the patients, although 20% of them required more than one catheter. Treatment was successful in all cases of lung abscess. These patients had been previously treated with standard medical therapy for 12 to 53 days without significant improvement in their clinical condition. Patients with empyema composed the largest group treated. Eighty percent (16 of 20) of them had a loculated (LOC) process. The LOC group appeared to have a slightly better success rate than did the non-LOC group (75 versus 50%, p = 0.33). When the catheters failed to resolve the problem (empyema, 6; chylous effusion, 1; malignant effusion, 3; and spontaneous pneumothorax, 1, either operation (9.1%) or a standard thoracostomy tube (13.6%) was required. The complications rate was 20%, but most of these were minor problems including pneumothorax, 5; catheter occlusion 3; fractured catheter, 1; infection, 1; and significant subcutaneous emphysema, 1.(ABSTRACT TRUNCATED AT 250 WORDS)