This article introduces a novel consultative method termed reconstitutive ethnography, considered useful for the in-depth description and analysis of the interaction between professional and client in the delivery of a health or social care program. The article contextualizes this method in process evaluation generally and specifically in what the author describes as exploratory process evaluation. Methods to study the interaction between professional and client are considered, culminating in a focus on so-called consultative methods that involve professionals in reflection on their practice. Reconstitutive ethnography, which integrates constitutive ethnography, critical incident analysis, and Delphi methods, is described and exemplified in evaluation studies undertaken by the author. Exploratory process evaluations are of value in evaluations to set standards, permit comparisons, facilitate causal analyses between delivery and outcomes, and allow for replication, and in research to contribute knowledge to the area of professional competence and its effectiveness.