1. High temperature annealing of rhodium catalyst wire followed by rapid cooling, increases the reaction rate of the hydrogenolysis of propane and the selectivity for CH4, in comparison to slow cooling, which in turn increases the selectivity for C2H6. 2. Annealing and cooling in hydrogen increases the activity of the catalyst at 573 K by 1.6 times more than annealing the catalyst in an inert gas. © 1988 Plenum Publishing Corporation.