Over an 8-year period, 1246 consecutive patients undergoing abdominal surgery were followed up postoperatively for a maximum of 5 years to study retrospectively the incidence, date of occurrence location and risk factors of incisional hernia. Only 1081 cases were assessable. Overall 94 incisional hernias (9%) were evidenced. The actuarial rate of incisional hernia was shown to be 13% at 5 years, occurring during the first 24 months in 80% of cases. Risk factors were analyzed according to four parameters: patient's status, underlying disease, surgical technique, postoperative complications. Morbid obesity, underlying disease, emergency surgery, wound or deep abscesses or early reoperation were all statistically significant factors. From the overall analysis of results it is shown that at 5 years 13% of patients at risk present postoperative incisional hernia. The two main factors on which surgeons are able to act preventively are the choice of incision site and the onset of wound abscesses. Subcostal incision is the most suitable and prevention of abscesses can be obtained essentially by antibiotic prophylaxis.