A remarkable collection of 298 Gambian Asilidae collected by William F. Snow between 1974 and 1977 and housed in the collections of the Oxford University Museum of Natural History is reported upon. Before this study only 19 catalogued species were known from this tiny West African country. Snow's collection has representatives of 55 species and apart from a new genus (Antiscylaticus) and five new species (Hippomachus snowi, Robertomyia snowi, Pegesimallus snowi, Storthyngomerus snowi, Antiscylaticus snowi), described in this paper, there are other species that will probably prove to be new to science. Three previously established Afrotropical genera (Hippomachus, Robertomyia, Scylaticus) are reported for the first time from West Africa. In addition, representatives of eight other genera, known to occur in West Africa, but never before recorded from Senegal or Gambia, are represented in Snow's collection (Ancylorhynchus, Gonioscelis, Habropogon, Leptogaster, Nusa, Oligopogon, Rhabdogaster, Stichopogon).