Abstract: The adjacency matrix A(G) of a graph G is the n\times
n matrix with its (i,j)-entry equal to 1 if v_i and v_j are
adjacent, and 0 otherwise. The spectral radius of G is the
largest eigenvalue of A(G). In this paper we determine the graphs
with maximum spectral radius among all trees, and all bipartite
unicyclic, bicyclic, tricyclic, tetracyclic, pentacyclic and
quasi-tree graphs, respectively.

Key words: bipartite graph, cycle;spectral radius