<b>On the Radio Number of Certain Classes of Circulant Graphs</b> Radio labelling problem is a special type of assignment problem which maximizes the number of channels in a specified bandwidth. A radio labelling of a connected graph G= V,E is an injection h V G N such that d x,y |f x f y | =1 d G x,y V G , where d G is the diameter of the graph G. The radio number of h denoted rn h , is the maximum number assigned to any vertex of G. The radio number of G, denoted rn G , is the minimum value of rn h taken over all labelling’s h of G. In this paper we have obtained the radio number certain classes of circulant graphs, namely G n {1,2… n 2 1} ,G n {1,n 2} ,G n {1,n 3} and G n {1,n 5} . Labelling, Radio labelling, Radio number, Circulant graphs 430-434 Issue-5 Volume-4 Kins Yenoke