Si/Si0.9Ge0.1 heterostructures have been analyzed using the Capacitance-Voltage (C-V) technique described by Kroemer. A valence band offset of approximately 70 +/- 10 meV was deduced, in good agreement with that predicted by other methods. The significant deep level populations revealed by deep level transient spectroscopy and variable temperature C-V methods have a comparatively small effect upon the deduced offset.