An assessment of ground-water withdrawals at municipal industrial parks throughout Puerto Rico was conducted to investigate the effect of ground-water usage on nearby surface- and ground-water resources. Water-bearing strata were divided into four generalized hydrogeologic units: (1) fissured aquifers (including karst and non-karst limestone); (2) intergranular aquifers; (3) intergranular aquifers overlying fissured rock units; and (4) strata with local or limited ground-water resources. Approximately 49 percent of the municipal industrial parks are located in areas with local or limited ground-water resources, 29 percent overlie intergranular aquifers, 13 percent overlie fissured aquifers, and 9 percent overlie intergranular units that overlie fissured rock units. Hydrogeologic data for the generalized hydrogeologic units were compiled from published U.S. Geological Survey reports. Depths to ground water near industrial parks range from approximately 20 to 400 feet in the fissured aquifers, 6 to 65 feet in coastal intergranular aquifers, 3 to 30 feet in intergranular aquifers overlying fissured rock units, and 1 to 100 feet in strata with local or limited ground-water resources. Aquifer transmissivities near industrial parks range from approximately 100,000 feet squared per day in the fissured aquifers to less than 100 feet squared per day in the strata with local or limited ground-water resources. Well construction data were compiled from published U.S. Geological Survey reports, drillers? logs, and unpublished reports. Specific capacity for wells near industrial parks ranges from approximately 100 gallons per minute per foot of drawdown in the fissured aquifer at Manati to approximately 0.1 gallon per minute per foot of drawdown in strata with local and limited ground-water resources at Bayamon. Reported well yields near industrial parks ranges from 2,800 gallons per minute in the intergranular aquifer at Santa Isabel to approximately 3 gallons per minute in strata with local and limited ground-water resources at Adjuntas. Historical ground-water-level data from U.S. Geological Survey observation wells were used to define ground-water levels trends in the vicinity of industrial parks. Areas showing ground-water level declines, and therefore possible aquifer over-development, are located in Barceloneta and Guayama. Rising ground-water levels were noted in the vicinity of industrial parks at Florida, Ponce, and Yauco. Ground-water withdrawal data were compiled from site visits to the industrial facilities and from information provided by Puerto Rico Department of Natural and Environmental Resources. Total ground-water withdrawal at the municipal industrial parks was estimated to be 1.6 million gallons per day. Most withdrawals were from intergranular coastal aquifers, which accounted for about two thirds of the ground-water withdrawals. Municipal industrial parks with substantial ground-water withdrawals are located in Bayamon, Caguas, Humacao, and Ponce.