The room temperature high cycle fatigue behaviour of stir cast AA 6061-SiCp composites, with varying reinforcement percentage, is studied. The specimens were tested under fully reversed cyclic deformation in the peak aged condition. Composite with 20% reinforcement exhibit superior fatigue strength over other composites (with 10,15 and 25% reinforcement). The experimental results are correlated with scanning electron micrographs of the failed specimens. Two distinct morphologies namely, crack initiation/ propagation and fast fracture region, were present. Mode-I type cracking was found to have dominated the crack initiation. The final fracture mode was found to be ductile with nucleation, growth and coalescence of cracks in the matrix.