The authors give results of a survey of arboviruses isolated from mosquitoes in the neighborhood of Yaounde, Southern Cameroon, from 1964 to 1972. During this period of nine years 127.520 female mosquitoes including at least 72 species were collected and processed for attempt of virus isolation. 55 strains belonging to 12 viral types were recovered from at least 19 species of mosquitoes. The appearance of different viruses over the years was quite intermittent. A possible reason for this is the need for viruses to move in search of susceptible vertebrate hosts. There was not definite evidence of vector host specificity except likely for Anopheles gambiae s. l. as a vector of Tataguine. However, among the more infected species, some ones show by their host preferences they could be true vectors of the viruses isolated from them.