A tritium input function for the Roswell artesian basin was constructed from tritium analysis of precipitation and ground water samples taken over 13 years, together with geohydrologic and meteorologic data. This recharge function, rather than tritium concentrations in precipitation, was correlated with tritium-time profiles of seven wells, which were also correlated among each other. Two distinct subregions, characterized by different circulation patterns, were recognized in the basin. The residence time of water in the northern subregion (Roswell) was about four years, and larger than seven years in the central region (Artesia). Tritium input characteristics varied from north to south along the western flank of the basin. Hydrological parameters computed on the basis of tritium data were correlated with lithologic and structural features in the basin. A one-dimensional dispersion model was successfully used to test the precipitation/recharge relation using tritium as a tracer. (Author Modified Abstract)