In the dog, massive proteinuria and/or the nephrotic syndrome have been commonly associated with renal amyloidosis and membranous glomerulonephritis. Primary glomerulopathies associated with the nephrotic syndrome in man also include minimal change nephrotic syndrome and focal glomerular sclerosis. A 4-year-old Collie dog is described with clinical, histological, immunohistological, and ultrastructural findings similar to those which characterize the minimal change nephrotic syndrome (MCNS) in man.