Organized glomerular electron-dense deposits with a fingerprint pattern are well known in some patients of lupus nephritis or cryoglobulinemia. In general, these two diseases are always discussed separately as the causes of such deposits. However, 3 of our 5 lupus patients with glomerular fingerprint deposits also had cryoglobulinemia. One of the remaining 2 patients died and the other was lost to follow-up. The purpose of our study was to seek an appropriate clinicopathologic assessment of fingerprint deposits. All these patients showed overt proteinuria, active urinary sediment, a high degree of activity of lupus nephritis, and diffuse proliferative glomerulonephritis (WHO class IV). Their cryoprecipitates and renal biopsy specimens were investigated by means of immunochemistry, immunofluorescence and electron microscopy. The ultrastructural ‘fingerprint’ structures were exactly the same in the cryoprecipitates and in the glomerular deposits in 2 of 3 lupus patients with cryoglobulinemia, as were IgG, IgM and IgA. Therefore, these observations furnish emerging morphologic evidence for the glomerular deposition of immune complexes of circulating cryoglobulins in lupus nephritis. In addition, electron microscopic fingerprint deposits on renal biopsy or cryoprecipitate can be regarded as a very sensible marker of concomitant or subsequent development of diffuse lupus nephritis. If the patient is accompanied by nephritic syndrome, an early trial of immunosuppressive therapy may be warranted.