The 2019 iteration of the ASCOBANS and ACCOBAMS joint best practice for cetacean stranding investigations and tissue sampling .Monitoring dead stranded cetaceans offers an often unique opportunity to gain insights into the health of, and threats and stressors affecting, marine ecosystems. Information derived from the systematic examination of stranded carcases can provide insights into the at-sea population not easily acquired through other means, indeed strandings data is the major source of information available for some species. Detailed investigation of carcases can assist in the determination of causes of death, offer surveillance on the incidence of trauma and disease and provide tissues and data for subsequent analysis into a range of biological and ecological parameters. The collection of data and samples for ancillary investigations over a range of disciplines can provide information on the general population ecology, helping countries evaluate and mitigate possible threats affecting species conservation and the marine ecosystem.Many EU countries operate cetacean strandings investigation networks as part of their obligations to international agreements. These include the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS), the Agreement for the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and contiguous Atlantic Area (ACCOBAMS), the EU Habitats Directive (NATURA2000), the OSPAR Commission and the Baltic Marine Environment Protection Commission (HELCOM). The Marine Strategy Framework Directive (MSFD) obliges the member states to develop indicators and descriptors for the surveillance of Good Environmental Status of cetaceans. Many of these strandings networks are well established and have long-term datasets comprising extensive biological and pathological information from the systematic collation and investigation of mortalities. In addition, many European strandings networks curate uniquely important tissue and pathogen archives. Most networks follow the original protocol by Kuiken and Hartmann, published in 1993. In the subsequent decades, stranding networks throughout Europe have developed, and new analytical techniques (e.g. assessment of the effects of barotrauma) or health impacts e.g. grey seal predation, have been incorporated into operational methods. The aim of this document is to update the protocol with the currently available techniques and methodologies agreed between all member countries of ACCOBAMS and ASCOBANS. It is hoped that this updated protocol can serve three overall aims:1.To provide a reference document for veterinarians and biologists currently engaged in cetacean post-mortem investigation, summarising a recognised approach to stranding investigation across European networks;2.To highlight areas where harmonisation of data from existing networks could allow for analysis and inference to be made between networks, of particular relevance for the transboundary, mobile species;3.Provide a start-up guide for researchers attempting to instigate new stranding monitoring programmes, particularly in regions of the world with limited resources for extensive, top-down surveillance programmes. It should be emphasised that this document is not designed to replace existing protocols, particularly those of longstanding and well-established laboratories and stranding networks, but offers a post mortem framework aiming for consistency across Europe when conducting examinations on dead cetaceans.