Niranjan, P.K.Kola, S.R.2020-03-312020-03-312020International Journal of Applied and Computational Mathematics, 2020, Vol.6, 2, pp.-https://idr.nitk.ac.in/handle/123456789/12381Radio k-coloring of a graph G is an assignment f of positive integers (colors) to the vertices of G such that for any two distinct vertices u and v of G, the difference between their colors is at least 1 + k- d(u, v). The span rck(f) of f is the largest number assigned by f. The radio k-chromatic number rck(G) is min{rck(f):fis a radiok-coloring ofG}. When k= diam(G) , f is called a radio coloring of G and the corresponding radio k-chromatic number is known as the radio number of G. In this paper, we determine the radio number of some classes of trees. Also, we find the radio d-chromatic number of infinitely many trees and graphs of arbitrarily large diameter constructed from trees of diameter d in some subclasses of the above classes. 2020, Springer Nature India Private Limited.Article