The refractive indices of perdeuterated hydrocarbons n-hexane-d(14), heptane-d(16), and octane-d(18), benzene-d(6), toluene-d(8), and ethylbenzene-d(10) have been measured at room temperature at five different wavelengths. The polarizabilities of these compounds have been computed as a function of wavelength using the Lorentz-Lorenz equation and at infinite wavelength using the Cauchy equation. In all cases, the polarizabilities of the deuterated compounds are less than the corresponding nondeuterated compounds.