The microstructure and dry sliding wear behaviour of XD(TM) ZL201-TiB2 in situ composite were studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, pin-on-ring friction and wear testing. The microstructural constituents of the ZL201-TiB2 composite aged at 175 degrees C for various ageing times were found to be dispersive submicrometre TiB2 particles, fine theta", theta＇-precipitates and a-Al solid solutions. As contrasted to the unreinforced ZL201 alloy, the ZL201-TiB2 composite possessed a higher microhardness and wear-resistance as well as a shorter ageing time for peak hardness. With the increase of sliding distance, transition of the dominant wear mechanism for the ZL201-TiB2 composite occurred from adhesive wear to fatigue wear in sliding contacts. At the earlier stages of wear, adhesive wear characteristics featured by mild scratchings and plastic smearing were observed on the worn surface and platelet-type wear debris; but at the later stages, contact fatigue failure of a relatively thick surface layer in relative motion, which revealed a build-up of layer-like structure and the presence of spherical particles of debris, became the dominant factor for the removal of composites.