To model the effects of control operations on possum populations it was first necessary to determine the basic parameters on which the model could be based. In the absence of definitive field data, a range of parameters was used to simulate the growth of possum populations at various rates of increase. The theoretical effects of different levels of control by sterilisation and conventional killing were then calculated. The modelling shows that permanent sterilisation of both sexes is more effective than killing the same proportion of the population. Temporary sterilisation is not as effective as killing. The implications of these findings are discussed in relation to future control of possums.