Optical heterodyne detection is implemented in an impulsive stimulated Raman scattering (ISRS) experiment by the use of a Mach-Zehnder interferometer. The combination of polarization-selective ISRS and heterodyne detection allows direct measurements of the real and imaginary parts of an arbitrary element of the third-rank material response tenser chi((3)). The heterodyne-detected chi(1111)((3))(t) of CS2 is presented and compared with the homodyne-detected response.