The improvement in the sensitivity of electron paramagnetic resonance spectrometers obtained when a parametric or maser preamplifier is inserted between the sample cavity and the detection system is examined. It is shown that the addition of such a preamplifier is justified only when the paramagnetic sample saturates at power levels of 0 (1) μW and the spectral purity of the microwave power oscillator is less than 1: 10⁶. It is concluded that the additional complexity of the system is seldom justified since the improvement in sensitivity cannot exceed a factor of 10^1/2 when the microwave diodes are operated with minimum noise figure. The same improvement in sensitivity can be achieved in the absence of saturation effects by increasing the oscillator power level by a factor of ten since the sensitivity is proportional to the square root of the sample cavity power.