Wistar rats rendered cirrhotic with carbon tetrachloride excreted significant proteinuria and hematuria. Serum levels of IgA and IgG were significantly elevated in cirrhotic animals. They showed mild mesangial proliferation and immunofluorescent studies revealed deposits of IgA and IgG predominantly in mesangial areas and along capillary walls. These findings were very similar to those seen in patients with hepatic cirrhosis or IgA nephropathy. The deposits of IgA were also found in hepatic tissue from cirrhotic animals. The intensity and distribution of glomerular IgA deposits were not diminished after treatment with acid buffer. These results suggest that glomerular IgA are IgA polymers and decreased hepatic clearance of hepatic IgA polymers may be responsible for the glomerular deposition of IgA.