A Monte Carlo simulation of the reaction to form antihydrogen by positroniu
m impact upon antiprotons has been undertaken. Total and differential cross
sections have been utilized as inputs to the simulation which models the c
onditions foreseen in planned antihydrogen formation experiments using posi
trons and antiprotons held in Penning traps. Thus, predictions of antihydro
gen production rates, angular distributions and the variation of the mean a
ntihydrogen temperature as a function of incident positronium kinetic energ
y have been produced.