This document discusses models for diagnosing organizations. It introduces the open systems model which views organizations as existing within an environment and exchanging inputs, transformations, and outputs. Key properties of systems like boundaries and feedback are also discussed. Several diagnostic models are presented for understanding organizations at the individual, group, and organization levels. The document emphasizes that diagnosis involves understanding each part of the model and assessing how well elements are aligned with each other and external inputs to impact organizational effectiveness. A number of other diagnostic models developed over time are also listed.