Two warmblood horses with a history of chronic weight loss and inappetence were referred to the Faculty of Veterinary Medicine, Ludwig-Maximilians University of Munich, Germany, for further examination. The clinical signs in horse 1 were fever, tachycardia and tachypnoea, and chronic ulcerative keratopathy of both eyes. Horse 2 had severe oral ulcerations and was coughing during feeding. In both horses, increased bronchovesicular sounds were heard during auscultation of the lungs. Laboratory findings included mild anaemia, lymphopenia and hypoalbuminaemia. Radiographic examination of the thorax revealed a severe nodular interstitial pattern. Multiple nodular lesions on the surface of the lung were observed by ultrasonographic examination. Light microscopy of lung biopsy specimens obtained from horse 1 revealed a severe chronic fibrosing interstitial pneumonia. Both horses were eventually euthanased because of a poor prognosis. Postmortem examination confirmed severe multinodular fibrosing interstitial pneumonia in both horses, and lung tissue yielded positive results for equine herpesvirus type 5 DNA using PCR assay. On the basis of the clinical, radiographic and pathological findings, as well as the PCR results, the diagnosis of equine multinodular pulmonary fibrosis was established.