The cytopathicity and susceptibility of prototype HIV-1 [HTLVIIIB] and Ghanaian HIV isolates [GH1, GH2, GH3] to inhibition by ddCyd and ddIno were determined by the tetrazolium-based colorimetric method. HIV-1 [HTLVIIIB] caused the most cytopathic effect followed by HIV-2 [GH2]. At low MOI, HIV-2 [GH1] was more cytopathic than HIV-1 [GH3] but the reverse was true at high MOI. Using EC90 concentrations for comparison at similar cytopathicities, both HIV-1 [HTLVIIIB] and HIV-1 [GH3] which belong to prototype HIV-1 group, were effectively inhibited by one or both drugs. In contrast, HIV-2 [GH1] which belongs to prototype HIV-2 group, and especially, the highly divergent HIV-2 [GH2] which belongs to HIV-2b group were relatively resistant to inhibition by ddCyd and ddIno.