The cellular kinetics of repair and scarring which occurs after induction of periportal necrosis in mice by allyl alcohol were examined by histology and immunohistochemistry. Thirty-six six-week-old female C57Bl/6J mice were injected intraperitoneally with two doses of allyl alcohol on day 0 and tissue sections were taken at various times and stained by haematoxylin and eosin or immunostained for proliferating cell nuclear antigen (PCNA), bile duct/oval cell marker A-6, and DNA fragments (apoptosis). Within 6 hours, periportal necrosis was seen extending to produce large zones of confluent, pan-acinar irregular necrosis, predominantly in the right and medial lobes with sparing of the left and caudate lobes. Restoration of liver mass was accomplished mainly by proliferation of mature hepatocytes in the surviving lobes of the liver (hyperplasia). In the right and medial lobes where necrosis was limited to the periportal zone, there was some, but much less, proliferation of small, oval periportal cells. The large necrotic zones in the right and median lobes shrank and were replaced by granulomatous inflammation. This cellular contribution of liver regeneration in the mouse was different from that previously reported in the rat and provides a means of inducing only a small proliferation of oval cells.