The microstructure of low-density (0.13-0.64 Mg m(-3)) carbon-carbon composites was investigated using optical microscopy, scanning electron microscopy and image analysis. All samples initially contained varying proportions of rayon precursor carbon fibres, recycled fibrous material and phenolic resin precursor matrix, and were manufactured utilizing a vacuum moulding technique. Some of the composites were densified using the chemical vapour deposition (CVD) of pyrolytic carbon. All the composites were shown to have a two-dimensional planar random microstructure, with a distinct layering effect being seen; on the microscopic (and sometimes macroscopic) level. The degree of layering in the composites was quantified utilizing image analysis and was found to be most pronounced in samples containing no recycled material, and least pronounced in samples containing all of its fibrous constituent as recycled material. The composites were found to be very porous, the pores consisting of mainly interconnecting open pores (typically 65-85% of the sample volume). In non-CVD samples the fibrous material was held together by thin (< 5 mu m) discrete "matrix bonds", with a few large (typically 100 mu m x 200 mu m x 800 mu m) fibre bundles also existing within the structure. In the CVD-processed material the deposit coat on the fibres was of even thickness throughout the composite and joined together fibrous material that was not previously in contact.