Immunotactoid glomerulopathy (ITG) demonstrates glomerular deposits that are characterized by highly organized ultrastructure. The deposits appear to be composed of immunoglobulin and complement that were negative for amyloid by Congo red stain. However, it has been difficult to distinguish the difference between ITG and fibrillary glomerulonephritis. In the present study, we performed an immunoelectron microscopic study to identify the factors that seemed to be associated with the glomerular deposits in a case of IgA-dominant ITG. IgA, light chain kappa and fibrinogen were colocalized in association with fibrillar deposits in the extracellular matrix of mesangial cells. Therefore, it is likely that the complex of IgA, light chain kappa and fibrinogen are associated with the formation of highly organized ultrastructural deposits in a case of IgA-dominant ITG.