The use of Spectral Variation Functions (SVFs) for Automatic Speech Recognition (ASR) is discussed. Two types of SVFs are compared and results for different SVF orders are presented. A 20% string error-rate reduction has been obtained on the 10 kHz TI/NIST connected digit corpus, by adding a fourth order SVF to a set of acoustic features made of S Mel scaled Cepstral Coefficients(MCC), their time derivatives, the normalized signal energy and its time derivative.