The burst abdominal wound has a mechanical cause. It is the results of suture breaking, knot slipping, the intact suture cutting out of the tissues or protrusion of gut or omentum between stitches. Measurements of abdominal girth and the xiphoid-pubis distance before and during abdominal distension show that a wound may lengthen by 30 per cent if distension occurs. An adequate reserve of suture length in the wound is necessary to allow this lengthening to occur and to ensure a minimal resulting rise in tension between the sutures and the tissues. Three variables present in every continuous wound closure--the suture length inserted, the wound fasical length and the number of stitches--determine the stitch interval and the size of the tissue bite, which are the two vital factors in wound strength under the surgeon's control. These variables may be expressed by the ratio of the length of suture (SL) inserted to the wound length (WL), the ratio SL:WL. Analytical and clinical evidence is presented to show that: 1. Deep wound disruption (evisceration and ventral hernia) is associated with the use of an SL: WL ratio of 2: 1 or less-the lower the ratio, the greater is the risk of a burst wound. 2. Wound disruption because of cutting out of sutures can be prevented by the use of non-absorbable continuous sutures at 1-cm intervals and an SL:WL ratio of 4:1 or more.