Iridium silicides have been prepared by annealing Ir films on (100) - and (111) -oriented Si from 300 to 500 °C. Phase identification was performed by both x-ray and electron diffractions, and Schottky-barrier height by current-voltage measurements. The silicide IrSi has been found to have a barrier height of 0.93 eV, which is the highest among all the silicides measured. The high value leads us to conclude that the silicide does not follow the linear relation which exists between barrier height and heat of formation of most other silicides.