The electron- and hole-mobility of Hg(BrxI1-x)(2) crystals with compositions x = 0.25, 0.50, 0.75 and 1.00 were measured using the time-of-flight method. The samples, in the form of thin layered plates, were irradiated with an Am-241 source; a memory oscilloscope monitored the corresponding current pulses created by the nuclear source. So the flight time and consequently the mobilities of the free electrons and holes were determined, and compared to results obtained on HgI2. (C) 2002 Elsevier Science Ltd. All rights reserved.