Pneumothorax (PTX) in patients with penetrating thoracic trauma is routinely ruled out with serial chest radiographs (CXRs). This study examined the efficacy of a shortened time period between initial and follow-up radiographs. Patients with penetrating torso injuries treated at a Level-1 trauma center received a CXR during their initial evaluation. If no pneumothorax or hemothorax was noted, and the patient did not require immediate admission to the Intensive Care Unit or operating room, a repeat chest film was taken at 3 and 6 h. Findings were treated as clinically indicated, and patients were discharged home if the last radiograph revealed no evidence of pathology. Over a 15-month period, 116 patients were evaluated for penetrating thoracic injuries (93 stabbings, 23 gunshot wounds) and had no pneumothorax detected on initial CXR. Two patients had pneumothorax detectable only by computed tomography. One patient had a normal initial CXR, but developed a PTX on the 3-h film, requiring tube thoracostomy. No patients developed a PTX on the 6-h study that was not present on the initial or 3-h CXR. In conclusion, extending the time between initial and final CXRs to 6 h in patients with penetrating thoracic trauma provided no additional information that was not available on the 3-h film.