The Woodbine aquifer is an important source of groundwater in north‐central Texas. In a survey of 63 wells located within or near the aquifer's recharge zone, nitrate concentrations ranged from less than 0.22 mg/L to 102 mg/L. Only one observation exceeded 45 mg/L. In general, nitrate concentrations were higher in shallower wells, and there was no significant correlation between nitrate and chloride concentrations. Potential sources of nitrate in the study area include fertilizers used on crops and lawns, animal waste from feedlots, and household wastewater. Results of this study suggest that nitrate concentrations are locally elevated above background levels, shallow groundwater is more susceptible to nitrate contamination, and fertilizer is a probable source of groundwater pollution. The use of deep wells and careful land use planning may alleviate future contamination of groundwater supplies.