An independent commission that evaluates and accredits about 18,000 healthcare organizations and programmes in the USA, reported that the number of operations performed on the wrong body site or the wrong patient has increased dramatically from 15 in 1998 to 150 in 2001. Orthopaedic/podiatric operations were the most common procedures linked to errors, accounting for 41% of the 126 cases that were analysed. General surgery procedures accounted for 20% of the cases, neurosurgery operations for 14%, and urologic surgery operations for 11%. The remaining cases involved other procedures such as dental/oral operations. Fifty-eight percent of cases occurred in an outpatient surgical setting, 29% in an inpatient operating room, and 13% in other inpatient settings. Most of the errors involved operations on wrong body parts or sites, but 13% involved operations on the wrong patient and 11% involved the wrong surgical procedure. A number of factors seem to increase the risk of surgical mistakes. Among these, emergency cases and physical characteristics of the patient -- such as morbid obesity or physical deformity -- were the most commonly cited.