SAM1 and AM1 calculations were carried out on 41 molecules for the purpose of comparing the ability of these semi-empirical methods to compute vibrational frequencies. For 442 vibrational modes, the results show that SAM1 reproduces all frequencies with an unsigned average error of 9.0% compared with 9.6% for AM1. The average signed error for SAM1 is less than 1%, while that for AM1 is about 5%. Except in the case of non-H atom stretching modes, the signed errors were near zero, indicating that no special scaling adjustment is needed. However, non-H atom stretching frequencies have highly systematic errors for both methods. The average signed error for SAM1 is + 14% which is quite close to the unsigned error at 16%. In such an obvious case, a systematic correction can be applied with some confidence. It can be said that the SAM1 non-H stretching frequencies are predicted to be too high by 14%, and should thus be scaled by a multiplicative factor of 0.86. A similar multiplicative correction of 0.15 can be applied in the case of AM1 to vibrations of this type.