Total internal reflection second harmonic generation (TIR SHG) has been used to study a series of neat n-alkane/water interfaces. The incident angle and polarization dependence of the SH response from these oil/water interfaces has been examined in detail and correlates well with theoretical predictions. Surface nonlinear susceptibility measurements suggest a significant degree of molecular ordering at these interfaces for all alkane/water systems studied. Of particular note is the higher degree of order observed for the alkane/water systems consisting of even numbered hydrocarbon chains relative to the odd numbered hydrocarbons. The results demonstrate for the first time the utility of using TIR SHG to measure properties of the liquid/liquid interface in the absence of any optical resonances and expand the range of systems which can be examined by SHG.