Skin alterations are often observed in cetaceans. They are helpful indicators for numerous skin diseases, parasites and injuries, as well as for malfunctions due to immuno-depression or accumulated contaminants in these marine mammals. The foundation firmm (Foundation for information and research in marine mammals) set up a database created over 16 years by opportunistic whale watching vessels in the Strait of Gibraltar from 1999 to date. Seven species of cetacenas are regularly observed. Photo diagnosis, together with knowledge on the history of numerous individuals provide with us data which will be evaluated with regard to macroscopically visible skin alterations. Diagnosing the alterations will provide important insights to assess the condition and the health status of these animals.