Unions, like other service industry and/or nonprofit employers, are uniquely dependent upon the performance of their human resources to ensure organizational success. Consequentl  unions have much to gain from adopting a more strategic focus in the management of their vital human talent. While some unions are moving toward greater sophistication in their internal HR practices (Clark and Gray, 2005), as a whole unions have been slow to embrace a strategic outlook on human resources and adopt HR practices that could improve union effectiveness and rejuvenate the union movement. In this paper, I identify and discuss internal organizational characteristics and external environmental factors that may influence the adoption of more sophisticated HR practices by labor unions. It is hoped that the framework that is suggested here can be used to launch research directed at understanding and improving the diffusion of good HR practices among unions that could subsequently improve both the efficiency and effectiveness of unions as institutions.