This paper describes six existing evaluator-auditor working formats and the conditions which foster credibility of evaluation findings. Evaluators were classified as: (1) member of project developmental team, accountable to project director; (2) independent internal evaluator, accountable to system in general but not to project directors, and (3) external evaluator, responsible by contractual agreement to system management. Auditors were classified as either external or internal to the system. Financial and temporal factors, human resources, and expertise are discussed as possible constraints to the assurance of credible findings for each of the six evaluator-auditor working relationships. (Author)