In 2004–2005 we undertook an investigation to determine the causes of death in moose found dead in Alaska. Intact moose carcasses that were found by department personnel or reported by the public that were not obviously due to human-induced trauma, underwent detailed postmortem examinations and histopathology. Additionally, moose with radiocollars that were detected in mortality mode were investigated when predation was not the proximate cause of death. Fifty-four moose were examined and a variety of diseases or parasites, some not previously reported in Alaskan moose, were discovered. A late winter cluster of mortalities, mostly in calves, had gross and histologic lesions of vasculitis and fibrinopurulent peritonitis. Other notable diagnoses include meningoencephalitis, peracute clostridial septicemia, metastatic malignant melanoma, mesothelioma, meningoencephalitis, fungal pneumonia, and pyometra with uterine rupture, severe pathology associated with rumen flukes in debilitated moose, copper deficiencies, degenerative myopathy/granulocytic myositis, granulomatous steatitis and perineuritis.