as we know, this is the first attempt to do this for any mammalian species on earth. The behavioral patterns listed have been recorded mostly for the M-group chimpanzees of the Mahale Mountains National Park, Tanzania, where we have been doing research since 19 5. However, we have made a great effort to add patterns described from other study-sites known to us only through articles, books and videos. This book is based on a previous ethogram that had neither video clips nor illustrations, but the glossary has been much expanded. Since 1999, videographic recording often has been used at Mahale for research on various topics, particularly social interactions, although earlier cinematographic records were occasionally made from 1971 onwards. We have compiled video clips for almost all of the