['Long-term pain is a common sequela of thoracotomy, occurring in approximately 50% of patients 2 years after thoracic surgery. Despite this alarming statistic, little is known about the factors responsible for the transition of acute to chronic pain. The aim of the present study is to identify predictors of long-term post-thoracotomy pain.', 'Follow-up was for 1.5 years for patients who had participated in a prospective, randomized, controlled trial of preemptive, multimodal analgesia.', 'Subjects were recruited from a tertiary care center.', 'Thirty patients who had undergone lateral thoracotomy were followed up by telephone, administered a structured interview, and classified according to long-term pain status.', 'Present pain status was measured by a verbal rating scale (VAS). Measures obtained within the first 48 h after surgery were compared between patients with and without pain 1.5 years later. These include VAS pain scores at rest and after movement, McGill Pain Questionnaire data, patient-controlled morphine consumption (mg), and pain thresholds to pressure applied to a rib contralateral to the thoracotomy incision.', 'Fifty-two percent of patients reported long-term pain. Early postoperative pain was the only factor that significantly predicted long-term pain. Pain intensity 24 h after surgery, at rest, and after movement was significantly greater among patients who developed long-term pain compared with pain-free patients. A significant predictive relationship was also found at 24 and 48 h using the McGill Pain Questionnaire. Cumulative morphine was comparable for the two groups. Pain thresholds to pressure applied to a rib contralateral to the incision did not differ significantly between the groups.'] Does acute pain after thoracic surgery predict long-term post-thoracotomy pain?