Surgery and trauma are recognised as important causes of chronic pain, although their overall contribution has not been systematically studied. This paper reports on the contribution of surgery and trauma to chronic pain among 5130 patients attending 10 outpatient clinics located throughout North Britain. Surgery contributed to pain in 22.5% of patients, and was particularly associated with the development of pain in the abdomen and with anal, perineal and genital pain. Trauma was a cause of pain in 18.7% of patients, and was most common in pain in the upper limb, the spine and the lower limb. Patients with chronic pain associated with trauma are on average younger than those with chronic post-surgical pain. Further, and unusually for pain conditions, the trauma patients show an excess of males over females. These findings indicate that it can be unhelpful for pain classification systems to combine surgery and trauma in a single category. The results also point to areas for potentially fruitful research into the aetiology of chronic pain. In particular, studies are needed to identify the operative procedures associated with the development of pain so that preventive measures can be implemented.