The aim of this study was to investigate the findings of clinical, haemotological, biochemical, histopathological, mycological and urine analyses and to evaluate the efficiency of itraconazole treatment in dogs experimentally infected with Aspergillus fumigatus. In this study, 25 healthy male dogs were used. The animals were divided into 3 groups: group I (control), group II (infected) and group III (treatment) consisting of 5, 10 and 10 dogs, respectively. Cyclophosphamide was injected into the dogs of groups II and III before the inoculation of A. fumigatus via intravenous (i.v.) route. Clinical findings of aspergillosis were developed after the second day following A. fumigatus inoculation. Three dogs died in group II. On the seventh day after the inoculation of the agent (PI), lymphocytosis, monocytosis, granulocytosis and leucocytosis were determined in groups II and III. However, the percentage of lymphocytes in white blood cells decreased. The red blood cell and platelet counts, haemoglobin and haematocrit values, glucose concentrations and the specific gravity of urine decreased while serum alkaline phosphatase activity, urea nitrogen, total protein, globulin, magnesium and phosphorus concentrations increased. Haematuria was observed in all dogs, and proteinuria, glucosuria and ketonuria were observed in some of them. Leucocyte and erythrocyte counts increased in the urine sediment. Aspergillus fumigatus was isolated from the urine, nasal swabs, lungs. kidney, liver, heart, spleen, nasal concha and lymphoid nodules of some of the dogs, while the hyphae of the agent and granulomatous inflammation were observed only in the lungs and kidneys by histopathological examination. The treatment of the animals started on day 10 Pl. Itraconazole, at 5 mg/kg body weight per day, was orally administered for 6 weeks. Four dogs died during the treatment period. At the end of the experiment, all of the clinical signs in the 6 surviving dogs had improved except for exophtalmus, miosis, an absence of pupillary reflexes and blindness in 2 dogs. Haematological, biochemical and urine analysis findings returned to close to normal values. It was determined that itraconazole treatment was effective in 6 dogs.