Reactive infiltration processing was investigated in the NiAl system using nickel-powder and nickel-wire preforms. Inhomogeneous microstructures were often obtained with powder preforms which had high surface-to-volume ratio, low permeability and irregular infiltration paths. Homogeneous NiAl could be obtained with nickel-wire preforms which had lower surface-to-volume ratio, higher permeability and regular infiltration paths. NiAl composites reinforced with short molybdenum fibers and long tungsten and sapphire fibers were also fabricated by reactive infiltration.