Incisional hernias represent one of the most frequent complications of abdominal surgery. The incidence is probably underestimated. The pathogenesis is complex and not fully understood, implying patient-related factors (i.e., collagen biochemistry, obesity, age) as well as technical factors, including, among others, wound infection, suture material, and types of incisions and closures. In this paper, the first of two, the authors review the literature emphasizing the current knowledge concerning the pathogenesis of incisional hernias. The second article is focused on the treatment.