Serological studies on five isolates of RYMV collected from the Ivory Coast (IC), Sierra-Leone (SL), Niger (Nr), Kenya (K) and Nigeria (N) indicated that these isolates are serologically related. Gel double diffusion and direct ELISA tests showed that the five isolates could be arranged into three serological groups here designated RYMV-N, SL-IC and K-NR. However, the ISEM studies did not reveal any clear grouping of the heterologous isolates tested.