This paper describes the methodologies adopted and the results obtained in assessing the groundwater resources of Metro Manila and Metro_x000D_ Cebu. Also some early and recent studies on the aquifer systems in the two metropolis are presented to draw some comparisons on the_x000D_ assessment and data acquisition methods and identify some gaps involved and the improvements needed. Some of the indicators used in assessing_x000D_ groundwater potential and associated problems include storage coefficient, transmissivity, safe yield, and salt water intrusion. The complex and_x000D_ expensive nature of actual field monitoring and analysis has encouraged the use of mathematical models in this study. Specifically, models adopted_x000D_ by NHRC and JICA were used and their respective capabilities, data requirements and modeling results for water balance are described. Although_x000D_ the two models have specific inputs unique to each model and the NHRC model used secondary 9 year data (i.e. 1982-1990) while JICA used_x000D_ one-year actual data (1990), the models gave similar results as far as recharge to groundwater and piezometric heads are concerned. It was_x000D_ found that Metro Manila gets an annual recharge of 206 MCM which is basically due to the high rainfall events during the wet season. Inflows from_x000D_ Laguna lake and leakage from MWSS distribution systems have been also identified as contributors to the recharge. It was also found that due to_x000D_ the over pumping of wells in some coastal areas in Metro Manila, sea water intrusion of aquifers is now becoming a serious problem. The same_x000D_ holds true in Metro Cebu where water for all types of uses comes from groundwater. That is why the annual recharge from rainfall to the aquifer of_x000D_ the Maghaway valley in Cebu amounting to be 1.4 MCM plus an additional inflow of 1.1 MCM coming from riverbeds, are believed to be insufficient_x000D_ to cover the increasing demand for water from all sectors of the society._x000D_ _x000D_ It is envisioned that a regional scale groundwater and environmental planning scheme for the two metropolis needs to be developed by linking_x000D_ the models with GIS so groundwater data base maps can be overlaid with land use, management practices, recharge distribution and mass_x000D_ loadings of chemicals. A follow-up study which will incorporate this methodology will provide a useful management tool for developing water_x000D_ resources on a regional scale.