Of the assumptions commonly used in continuous infection model, the least likely to be even approximately true in large population, is that of homogeneous mixing. In this paper, We investigate a model for the spread of infection amongst a population which is divided into classes, such that the individuals of each class mix homogeneously amongst themselves, but mix to a lesser degree with individuals of other class. The stochastic model in this form is intractable and approximations are made, yielding results in reasonable agreement with simulation trials.