We present a new analytic fluid-phase equation of state (EOS) of binary nonadditive hard sphere mixtures having equal collision diameters (d(11)=d(22)=d) between like species, but having an unequal collision diameter (d(12)) between unlike species. For this purpose, we have generated EOS data by Monte Carlo simulations over a wide range of density, composition, and d(12) The analytic EOS produces reliable results for d(12)greater than or equal to d and d(12)d.