Measurements obtained between 1968 and 1976 indicate the influence of climatic factors and soil characteristics on soil moisture and production of perennial vegetation in the northern Mojave Desert. Seasonal distribution patterns of precipitation strongly affect plant-available soil moisture, and these patterns are, in turn, reflected in net production of perennial vegetation. Available climatic data and soil characteristics were used as input to a continuous simulation model to calculate the water balance for a unit area watershed. Computed and measured soil moisture agreed well over a range of values from close to the wilting point to near field capacity. Computed evapotranspiration rates were used to estimate water use by perennial vegetation. Computed water use was multiplied by a water use efficiency factor to estimate net production of perennial vegetation. Estimated net production exhibited year-to-year variability comparable with measured values, and agreed quite closely with available observations. Soil-water-plant relationships in the northern Mojave Desert are described briefly and an application is illustrated of a continuous simulation model to predict soil moisture and net production of perennial vegetation. Based on the analysis, the simulation model appears to have potential for estimating the water balance and above ground net primary production on arid and semiarid rangelands.