The microstructure-property relationships have been studied in B4C-beta SiC materials for boron contents from 0 to 30 wt.% (corresponding to a range from 0 to about 45 vol.% of B4C). The materials were produced by sintering or hot-pressing of composite B-Si-C powders synthesized by solid combustion. In order to characterise the microstructure quantitatively, observations of polished sections of the materials, etched by potassium salts, were made by using the scanning electron microscopy, After binarisation, the data were eventually subjected to image processing. For both coexisting phases (beta SiC and B4C) the distribution and mean values of the following microstructural parameters were determined : grain area, grain aspect ratio and grain dimensions. The electrical resistivity and bending strength were also determined for the materials characterised microstructurally.