Abstract. We present a non-linear mathematical model which analyzes the
spread of smoking in a population. In this paper, the population is divided into
ve
classes: potential smokers, occasional smokers, heavy smokers, temporary quitters
and permanent quitters. We study the e¤ect of considering the class of occasional
smokers and the impact of adding this class to the smoking model in [1] on the
stability of its equilibria. Numerical results are also given to support our results.