Fibroblastic cell cultures were derived from the hernial sac and some of the surrounding muscles (rectus sheath, internal oblique, and/or cremasteric muscle) of 130 Saudi patients with different types of herniation, and from 21 control subjects. The rates of cell proliferation were studied for 39 days. Results suggested decreased rates of proliferation of cells derived from patients compared to controls. In vitro studies of the rates of incorporation of 14C proline into the muscle biopsies revealed decreased rates of label incorporation in the samples derived from patients compared to controls. However, no differences were detected between rates of collagenase activities of the biopsies obtained from patients compared to those of controls. These findings suggest that collagen synthesis is probably defective in the studied group of Saudi patients with hernia.