The U.S. Environmental Protection Agency, through the Urban Institute, and in cooperation with the Tampa Bay National Estuary Program (TBNEP), has sponsored this project to investigate the technical feasibility of developing a Bay Quality Index (BQI) for Tampa Bay. The project objective was to develop a framework, or conceptual design, for a BQI that includes components for a variety of bay attributes, including physical, chemical, and biological characteristics of the bay. The conceptual approach to calculating a BQI includes four steps: (1) ranking data for each variable into classes ranging from very poor to excellent, whereby each was assigned a value from 1 (very poor) to 5 (excellent); (2) combining class values for each bay attribute into a Score; (3) calculating a sub-index from 0 (worst) to 10 (best) based on the Score for each bay attribute; and (4) combining sub-indices calculated for all bay attributes into a single BQI representative of overall bay quality. Three methods for ranking variables were examined: (1) a Subjective method through use of professional judgement; (2) an Objective method based on the frequency distributions of the existing data; and (3) a mixed method based on state water quality standards and frequency distributions of existing data. Example calculations of water quality index values were compared to reported EPC water quality index values and were found to be consistent with respect to trends with time for each bay segment.