A fraction (ui) of the body’s CD4 T cells are assumed to be in each compartment (u0 + u1 = 1) and the production rate of uninfected CD4 T cells in the body is apportioned between the drug sanctuaries (Λu0 day-1) and the main compartment (Λu1 day-1). In the absence of antiretroviral therapy, susceptible cells (Xi) within each compartment become infected cells (Yi) at a rate equal to the product of the density of infected cells in the same compartment (Yi/ui day-1) and the transmission parameter β. This assumption ensures that the basic reproductive number of each compartment, if it were isolated (i.e. in the absence of traffic of cells between compartments), is not directly related to the size of the compartment. Antiretroviral therapy blocks a fraction, zi, of these infections. The parameter zi is allowed to vary between compartments, with z0 ≪ z1 ≈ 1, so that antiretroviral therapy is highly effective in the main compartment. In the absence of trafficking therapy, cells travel from compartment i to the other compartment at a per cell rate of τi day-1. The constraint, τ0u0 = τ1u1, ensures no change in compartment size in the absence of infection. The envisaged trafficking therapy that we focus on acts to increase trafficking in both directions by a factor κ. In adaptations of this model discussed later, we also model trafficking therapy that independently manipulates the rate that cells flow into or out of drugs sanctuaries. Infected cells in compartment i are cleared at a per cell rate of δi day-1. These rates are free to vary between compartments to account for the possibility that drug sanctuaries may also be subject to impaired infected cell clearance rates (δ0 < δ1).