The power differential between practitioner and client is examined by reviewing empirical studies, professional practice frameworks and related legal and procedural questions, in the context of complaints about health professionals. Professional regulatory bodiesincluding ethics committees, association boards, and government licensing authoritiesoversee the ethical behaviour of professionals, specifically monitoring their use of power. Complaints which these regulatory bodies address are generally framed in terms of the way that power is used poorly or harmfully by a practitioner. Alleged ethical breaches are usually evaluated from a specific epistemological premisethe existence of a power incline between practitioner and client. We explore some alternative perspectives regarding the power that clients hold, in the process exposing assumptions about the question of harm done. Linear views of causality and responsibility are questioned, and it is suggested that a more complex understanding would better serve investigatory processes. This discussion does not delve into the psycho-dynamics underlying the complaints process, but rather addresses the operation of regulatory bodies in terms of perceptions of power differences in the professional relationship.