Background: Incisional hernia is the most frequently seen long term complication after laparotomy causing much morbidity and even mortality. The overall incidence remains 11-20%, despite studies attempting to optimize closing techniques. Two patient groups, patients with abdominal aortic aneurysm and obese patients, have a risk for incisional hernia after laparotomy of more than 30%. These patients might benefit from mesh augmented midline closure as a means to reduce incisional hernia incidence. Methods/design: The PRImary Mesh Closure of Abdominal Midline Wound (PRIMA) trial is a double-blinded international multicenter randomized controlled trial comparing running slowly absorbable suture closure with the same closure augmented with a sublay or onlay mesh. Primary endpoint will be incisional hernia incidence 2 years postoperatively. Secondary outcomes will be postoperative complications, pain, quality of life and cost effectiveness. A total of 460 patients will be included in three ar Disccusion: The use of prosthetic mesh has proven effective and safe in incisional hernia surgery however its use in a prophylactic manner has yet to be properly investigated. The PRIMA trial will provide level 1b evidence whether mesh augmented midline abdominal closure reduces incisional hernia incidence in high risk groups. Trial registration: Clinical trial. gov NCT00761475.