2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/108823We give an upper bound on the maximal eigenvalue of the adjacency matrix of a connected graph in terms of its maximum degree, diameter and order. This bound is best possible up to a constant factor and improves prevoius results of Stevanovic, Zhang, and Alon and Sudakov.Combinatorics15A42text