O'nyong-nyong (ONN) virus first appeared nearly 20 years ago and was responsible for one of the largest arbovirus outbreaks ever documented. Since the original outbreak ended, ONN activity, as determined serologically, gradually declined on the Kano Plain in western Kenya. In June, 1978, a virus similar or identical to ONN was isolated from a pool of Anopheles funestus Giles captured at Ahero on the Kano Plain. The possible implications of this isolation are discussed.