This work focuses on evaluation of the performance of a monolithic, versus standard packed bed, second stage regenerator in a Gifford-McMahon cryocooler. The monolithic, or bonded regenerator bed is made by means of a low temperature epoxy bonding technique developed [Adv. Cryog. Eng. 43B (1998) 1597] and optimized [R. Williamson, Individual Project Report, CFS, University of Victoria, 2001] by the Cryofuel Systems Group (CFS). Regenerator properties and results of several detailed load and no-load tests of the conventional packed bed regenerator and its monolithic form, using two different first stage regenerators, are presented. The monolithic regenerator performs as well as the standard one, despite a slightly higher-pressure drop observed. Analysis of this phenomenon is presented. (C) 2003 Elsevier Science Ltd. All rights reserved.