Simulation can be an effective tool for investigating the demography of small, prehistoric Southwest Pueblo communities. The model presented here incorporates biological and physiological, cultural, and behavioral characteristics and tracks each individual as the simulation of a small population is carried forward through 70 years of annual iterations. Sensitivity analyses are performed for a suite of critical parameter values. Many of parameters and functions are probabilistic, and Monte Carlo techniques are used to obtain statistically significant results. Simulation results are collected on numerous variables that profile the individual and group characteristics such as mortality, immigration to emigration ratio, nuclear family formation, and distribution of population size and mix. Initial success is dependent on the attributes of the founding population and its gender mix. The long-term survival of a small population is extremely sensitive to the mortality schedule, attributes of the founding population, and marriage-residence rules. Small shifts in the age-specific mortality statistics dramatically affect the population growth and the frequency of site collapse. The consequences of inaccuracies in mortality statistics are highlighted.