Fernández, A., Arbelo, M., Degollada, E., André, M., Castro-Alonso , A., Jaber , J.R., Martín, V., Calabuig, P., Castro, P., Herraez, P., Rodríguez , F., Espinosa de los Monteros, A. Pathological Findings in Beaked Whales Stranded Massively in the Canary Islands (2002). 17 th Annual Conference of the European Cetacean Society , Las Palmas de Gran Canaria, 2003 Resum: From September 24th to 27th, a mass stranding of 14 beaked whales occurred on the beaches of Fuerteventura and Lanzarote islands (Canary Islands-Spain). Seven animals (one female Mesoplodon densirostris, one female Mesoplodon europaeus and five male Ziphius cavirostris) were found dead the 24th of September, while the rest of the cetaceans were returned to deeper waters alive. Four more beaked whales were found dead the following days (25th and 27th). The necropsy of six fresh animals was performed the 24th, preserving the heads at 4ºC, until they were carefully analysed the 25th, in the Department of Veterinary Pathology (Veterinary School-University of Las Palmas de Gran Canaria). One male Ziphius cavirostris moderately autolitic was completely necropsied the 25th in Fuerteventura and three autolitic carcasses of two males and one female Ziphius cavirostris were analysed the 25th (Lanzarote) and 27th (Fuerteventura) respectively. We systematically took samples from all necropsied cetaceans and all of them were processed for their corresponding histopathological study. The epidemiological data, the gross and the histopathological results revealed that the ten animals died within the 24 hours period which would span a 6-12 hours prior to and after the appearance of the first stranded beaked whale, at around 7 am, 24th of September, 2002. At necropsy, all animals but one were in very good condition, and the macroscopic and microscopic studies of organ and tissue samples discarded previous existence of either degenerative, inflammatory and neoplastic processes or lesions related to injury caused by ships, fishing gear or other objects. On the other hand, the amount of gastric content, its freshness and digestive status reinforce that the period between the action of the "death-causing agent" and the death itself was short. We describe a mass stranding involving beaked whales showing a very characteristic and unusual pathological picture that coincided temporally and spatially with ongoing naval military manoeuvres.