We report a 67-year-old male patient who suffered from nephrotic syndrome and progressive renal dysfunction with monoclonal gammopathy (IgMkappa). Renal biopsy demonstrated amyloid deposition in glomeruli. Immunohistochemical studies of the renal amyloid using a number of antibodies, including anti-lambda and anti-kappa light chains, AA, beta(2)-microglobulin, and transthyretin, showed negative findings. Biochemical analysis of the deposited amyloid fibrils in gastroduodenal mucosa revealed that the amyloid fibrils were composed of an immunoglobulin heavy chain variable region (VH) fragment belonging to the VH1 subgroup, and a diagnosis of AH amyloidosis was made. In our institute, three patients with AH amyloidosis including the present one have been identified during the past 2 years, so AH amyloidosis seems to be by no means a rare disorder.