T [M] provides concentration-dependent neuroprotection against synergistic neurotoxicity of HIV proteins with cocaine (Coc); DHT's [M] neuroprotection is limited. Control conditions of incubation with Locke's Buffer vehicle or the HIV proteins or Coc only produced similar neuronal death. (Top Panel) Significant interaction of the HIV proteins with Coc, as illustrated by the lines diverging from parallel, produced toxic synergism (*p < 0.0087) (Middle Panel). T provides significant concentration-dependent neuroprotection against HIV proteins w/ Coc toxic synergism (#p < 0.0001). (Bottom Panel). DHT mediated partial protection against synergistic neurotoxicity of HIV proteins w/ Coc (#p < 0.023); however, the neuroprotection was not concentration dependent.