Preliminary examination of the aquifer in the vicinity of Portales, New Mexico, indicated the presence of coliform bacteria within a two mile radius of the town of Portales. The presence of these bacterial organisms in the water table at Portales is indicative of recharge to the aquifer. The study has examined both chemical and bacterial parameters of the aquifer and extended the results to elucidate any possible seasonal variations and sources of the pollution in the ground water. Bacterial and chemical analyses were done. Chemical analyses included nitrate, pH, and phosphate. Bacterial analyses were performed using membrane filter techniques. Both bacterial and nitrate contamination was found in varying amounts in most wells sampled and a correlation between the two was established. A relationship was found to exist between nitrate concentration and rainfall during the summer sampling interval.