The ultimate tensile strength of newly apposed tissue is the sum of the strength of the physical construct holding the tissues and the strength of biologic healing. For successful incisional hernia repair, the total strength of the repair must remain greater than the forces applied. While much work has been done to understand the science of wound healing-the ability of an open defect to contract and close-far less has been done to understand the healing of 2 newly approximated previously nonwounded surfaces held together with sutures or other implants. In this article, the elements of ultimate tensile strength on laparotomy closure as well as their progression over time will be related to clinical studies of abdominal wall closure.