The performance of a cw HF chemical laser master oscillator with power amplifier was measured as a function of input power, oscillator/amplifier flow field match/mismatch and location of the optical axis of the input beam. The amplification ratio is an inverse function of the input power (intensity) and, for maximum amplification, the peak of the intensity distribution must be matched to the peak of the zero power gain distribution in the amplifier. The match/mismatch of the oscillator/amplifier flow fields has a second order effect on amplifier performance. The measured Pout versus Pin performance curve showed that, after a continuous increase, the difference Pout-Pin remained almost constant over a wide range of input powers and that about one third of a device's oscillator output must be input to obtain amplifier output equal to the device's oscillator performance. When the input beam contained time-dependent oscillations, the amplitude modulation of the output beam was reduced by a factor that equaled the amplification ratio of the amplifier; the amplifier had no effect on the period (frequency) of the oscillations of the input beam. An amplifier performance model that predicts a device's amplifier performance given the device's oscillator performance as a function of reflectivity was developed. Excellent agreement between model predictions and experimental data was obtained. The model was used to predict multiple pass amplifier performance. The results showed that, with a two pass amplifier, one oscillator could drive six amplifiers. When the amplifier performance curves were plotted in terms of ζout versus ζin, where ζ=PAMP/POSC, the curves for different devices collapse to one.