We developed a competitive enzyme immunoassay for serum type IV collagen peptide as a marker of fibrogenesis, and examined the relationship between serum type IV collagen peptide and hepatic disorder in CCI, treated rats. The rats were treated for 8 weeks and signs of liver damage began to appear from about week 2. With the progression of these signs to liver fibrosis, type IV collagen increased in the fibrous septa and especially in the perisinusoidal walls, where the increase was manifested as development of a real basement membrane beneath the sinusoidal endothelial cells. In CCI4‐treated rats, serum type IV collagen peptide significantly increased with the progression of liver fibrosis. When CCI4administration was stopped, the collagen peptide rapidly decreased without any rebound rise. An intimate relationship was found between the production of serum type IV collagen peptide and liver prolyl hydroxylase activity and the amount of collagen deposited in the liver. These results suggest that serum type IV collagen peptide will be a uset ul biochemical marker for the early detection of fibrogenesis in the live