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Drug resistance to single therapeutic treatment in HIV infected individuals has promoted research into combined treatments. In this paper we propose a stochastic model under combined therapeutic treatment by extending the model of HIV pathogenesis under treatment by anti-viral drugs given in [Perelson AS, Neumann AU, Markowits M, Leonard JM & Ho DD, 1996, HIV-1 dynamics in vivo virion clearance rate, infected cell life span, and viral generation time, Science New Series, 271, pp. 1582{1586]. Variance and co-variance structures of variables are obtainable via this approach in addition to the mean numbers of free HIV, infectious free HIV and non-infectious free HIV that were obtained by Perelson et al. Comparing simulated data for before and after treatment indicates the importance of combined treatment and its overall effect(s).