Abstract. In this report a 9-year-old female German Shepherd dog with a membranoproliferative glomerulonephritis (MPGN) type III associated with concomitant infection of Dirofilaria immitis and Leishmania infantum is presented. Light microscopic evaluation of kidney revealed a diffuse hypercellularity and thickening of glomerular basement membrane. Heavy and coarse granular complement C 3 deposition and a weaker positive reaction to immunoglobulin G were present along peripheral glomerular basement membrane and in the mesangium in the immunofluorescent study. Transmission electron microscopy revealed deposits in the mesangium, subendothelium, and subepithelium. These lesions are compatible with membranoproliferative glomerulonephritis type III in humans.Key words: Dirofilaria; dogs; Leishmania; membranoproliferative glomerulonephritis; transmission electron microscopy.Membranoproliferative glomerulonephritis (MPGN) is a histologic lesion characterized by intraglomerular hypercellularity (mesangial cells, endothelial cells, and inflammatory cells), matrix expansion, and thickening to the walls of the peripheral capillary loops. Immunocomplex deposits in the capillary walls and within mesangium are seen on electron microscopy. Membranoproliferative glomerulonephritis is usually associated with an immune complexmediated pathogenesis and may be idiopathic (primary) or secondary to viral, bacterial, and parasitic infections. According to the World Health Organization classification, MPGN is subdivided, based on ultrastructural alterations in the glomerular basement membrane (GBM), as type I (subendothelial deposits), type II (intramembranous dense deposits), and type III. 6,7 In MPGN type III, immune deposits are found in the subendothelial and mesangial region, similarly to type I; in addition, numerous subepithelial deposits are present. 1,6,7,13,14 This work describes the features of MPGN type III in a dog associated with simultaneous infection with Dirofilaria immitis and Leishmania infantum. To the authors' knowledge, this is the first description of MPGN type III in dogs.A 9-year-old female German Shepherd dog was referred with a 4-week history of poliuria/polydipsia, anorexia, vomiting, and diarrhea with melena. A hematologic evaluation 3 days earlier had revealed blood urea nitrogen increase and elevated serum creatinine and antibodies to Leishmania spp. (IFAT 10 ) and D. immitis antigens (SNAP a ). On clinical examination, the animal was in lateral recumbency with a severely dull and depressed mental state (uremic status). Its body condition score was poor, and it exhibited generalized muscle atrophy, tachypnea (60/min), and tachycardia (170/min). Mucous membranes were dry and a pale-yellowish color while all lymph nodes were subjectively normal to decreased in volume. After blood and urine collection and fine needle aspiration of lymph nodes, the dog was hospitalized. Fluid therapy (lactated Ringers) was infused, and antiemetic and gastro protective therapy (metoclopramide, ranitidine) was initiated. Hema...