Exploration of an important paleoanthropological site in the Rift Valley of eastern Zaire, from over two million years ago to the present. The Semliki Research Expedition, directed by Noel T. Boaz, Curator of Biological Anthropology at the Virginia Museum of Natural History, has investigated the upper reaches of the Semliki River Valley since 1982. Nineteen papers by members of the Expedition present & discuss the geology, paleoecology, paleontology, & archaeology of the site. Includes documentation of presence of early hominids in the Western Rift over two million years ago; an extensive fossil flora, the first recovered from this area of Pliocene Africa & one that shows the nearby presence of dense, lowland forest; an extensive vertebrate & invertebrate fauna that documents the presence of savannas & which includes evidence of extensive evolutionary radiations of fish & molluscan species; the first relatively complete human fossil crania from the highest statigraphic levels; studies on the archaeology of the Age of Metals, ethnoarchaeology among the tribal groups inhabiting the area today, & actualistic studies, relevant to paleoanthropological interpretation.