There are spatial and temporal links between some mass strandings of cetaceans — predominantly beaked whales — and the deployment of military sonar^{1, 2, 3}. Here we present evidence of acute and chronic tissue damage in stranded cetaceans that results from the formation in vivo of gas bubbles, challenging the view that these mammals do not suffer decompression sickness. The incidence of such cases during a naval sonar exercise indicates that acoustic factors could be important in the aetiology of bubble-related disease and may call for further environmental regulation of such activity.

1. Institute of Zoology, Zoological Society of London, Regent's Park, London NW1 4RY, UK
2. Histology and Pathology Unit, Institute for Animal Health, Veterinary School, Montana Cardones-Arucas, University of Las Palmas de Gran Canaria, Gran Canaria, Spain
3. Wildlife Unit, SAC Veterinary Science Division (Inverness), Drummondhill, Stratherrick Road, Inverness, IV2 4JZ, UK
4. Department of Veterinary Pathology, University of Liverpool, Leahurst, Neston, Wirral CH64 7TE, UK
5. SAC Veterinary Science Division (Edinburgh), Allan Watt Building, Bush Estate, Penicuik, Edinburgh EH26 0QE, UK

Correspondence to: A. Fernández¹ Email: afernandez@dmor.ulpgc.es