Computer studies have been carried out to study the role of electron and hole saturation currents on the microwave and millimetre-wave performance of a GaAs double drift region (DDR) IMPATT. It has been found that (i) the device negative conductance and (ii) the device negative resistance both decrease with increase of either electron or hole saturation current, i.e. with the decrease in either electron or hole multiplication factor. It has also been observed that the frequency of operation shifts upwards and the device quality factor increases gradually with increasing saturation current. It has further been observed that the upward shift in operating frequency is more when the GaAs DDR IMPATT performance is controlled by the hole saturation current rather than by the electron dominated saturation current. The relative predominance of the hole saturation current over the electron saturation current in inducing the higher frequency shift of the GaAs DDR IMPATT may be explained in terms of the inequality of hole and electron ionization coefficients in GaAs. © 1991 Taylor & Francis, Ltd.