The present invention provides methods and compositions for determining whether a subject would benefit from co-receptor inhibitor therapy. In certain aspects, the methods can be used to determine whether a subject infected with a dual -mixed tropic population of HIV would benefit from CCCR5 -inhibitor therapy or CXCR4-inhibitor therapy, the methods comprising determining whether the HIV population is a homogeneous or heterogeneous population of HIV, wherein the nature of the homogenous or heterogenous population of HIV indicates whether the patient would benefit from co-receptor inhibitor therapy.