Most HRD practitioners are, or wish to become, actively involved as strategic business partners of managers, particularly with respect to helping them bring about effective and beneficial organizational change within their own organizations, or within host organizations. This article discusses the complexities of HRD related process issues in the effective management of organizational change, and the value of using HRD-related theory, change management-related theory, and/or academically rigorous internal in-company research to help inform, shape, and evaluate the change agency practice of HRD professionals and the managers they partner. Following a discussion of why many organizational change programmes fail, the author argues that 'evidencebased HRD' geared to the strategic thrust of the business will likely lead to the HRD function maximizing its contribution to organizational effectiveness and sustainable business success. Two UK case examples of evidence-based HRD are presented, followed by a discussion of the worth of 'professional partnership' research and empirical generalization 'replication' research.