As occupational therapists become increasingly concerned with accountability, the paucity of adequate instrumentation available for documenting therapeutic effectiveness surfaces as a major problem. Therapists will need to construct new or refine existing instruments to satisfy the requirements of third-party payment. The purpose of this paper is to illustrate how a new instrument is planned, developed, and validated. A sequential step-by-step process is illustrated with a flowchart and applied in the hypothetical construction of an attitude scale to assess school administrators' valuing of the role of occupational therapists in the schools. This example is provided to show how general psychometric principles are applied within an occupational therapy context.