Scanning electron microscopy (SEM), polarized light microscopy, transmission electron microscopy (TEM), and scanning acoustic microscopy (SAM) techniques have been used to characterize the microstructure of a self-lubricating film of polyacrylonitrile (PAN)-based fiber-reinforced mesophase pitch-based matrix carbon-carbon composites. The results indicated that the worn surface was covered with a smooth and dense lubricative film and the basal plane orientation of the lubricative film was randomized. The wear-induced amorphous film was identified by the diffuse rings/halos in selected-area diffraction (SAD) patterns, while the numerous SAD patterns of graphite structure on the worn surface were also observed. SAM shows the lubricating film formed by some delaminated wear debris which was compacted, rolled and piled up layer by layer. (C) 2002 Elsevier Science B.V. All rights reserved.