The determination of the diameter of an interconnection network is essential in evaluating the performance of the network. Parallelogramic honeycomb torus is an attractive alternative to classical torus network due to smaller vertex degree, and hence, lower implementation cost. In this paper, we present the expression for the diameter of a parallelogramic honeycomb torus, which extends a known result about rhombic honeycomb torus. © 2005 Elsevier Ltd. All rights reserved.