The grim scenario created by the AIDS epidemic has driven researchers to develop mathematical models to improve our understanding for the mechanisms responsible for HIV (the etiological agent for AIDS) transmission and of the evaluation of possible intervention measures. Recent reviews of the literature on models include those of [A1,A2], [CC1,CC2], and [SchCCH]. Some of the important conclusions generated by mathematical models include the clear identification of three key mechanisms which have the greatest effect on HIV transmission at the population level: variable infectivity, mixing or pair formation, and long, variable periods of infectiousness. For an extensive in depth study of some of the most recent mathematical and statistical work in these and other areas to AIDS epidemiology see [CC2].