The original Circuit Fix-It Shop spoken natural language dialog system was developed in order to validate an integrated model of dialog processing that enabled the following behaviors: (1) collaborative problem solving, (2) subdialog completion and movement, (3) contextual interpretation, (4) user-dependent response generation, and (5) mixed-initiative interaction. The goal of empirically validating a dialog processing model necessitates an awareness of computational constraints and robust error handling techniques as well as familiarity with past experimental studies on discourse behavior (usually of the human-human or simulated human-computer variety). Empirical study is beneficial in acquiring knowledge about how human linguistic behavior during interaction with a computer may differ from what would occur if the interaction was with another human. A similar approach is being attempted in followup work on the prevention, detection, and repair of miscommunication. The biggest deficiency of the original model (and reflected in the performance of the Circuit Fix-It Shop) is its general inability for dealing with miscommunication. In the current project we have studied previously recorded human-human and humancomputer dialogs in order to investigate strategies for reducing miscommunication in natural language dialog.