The Thirteenth Annual Conference of the European Cetacean Society was held at the Palau de la Musica in Valencia, Spain between 5th and 8th April, 1999. It was attended by 325 persons from 29 countries. The theme of the conference this year was "Marine mammal conservation for the new millenium". Contributions have been arranged broadly by subject, and within subjects, they are arranged alphabetically. All abstracts were subject to a review process and represent all those submissions which were accepted for the conference. Extended summaries have been edited to improve clarity and to maintain a uniformity of presentation.