The mechanical properties of reinforced thermoplastics depend on such characterisitcs of the filler as granulometry, orientation and dispersion. These different microtextural parameters were determined by using a single tool: image analysis, which was coupled with optical and electron microscopies. The different materials tested were based on short-glass-fibre-reinforced polypropylene obtained by extrusion and injection steps. For the different samples analysed, the processing conditions and the filler concentration were constant, and variability was due to the different average lengths of the filler incorporated in the matrix. The different filler parameters were determined with particular emphasis on the techniques of dispersion characterisation. The techniques developed in this study were based on image analysis. They enabled us to estimate filler-size distribution and developement of the three-dimensional orientation inside the material and between different samples. The development of the filler dispersion was also made apparent. In addition, the relationships obtained between the different microtextural parameters were investigated. The general conclusion is that image analysis is very suitable for characterisation of this kind of material., The mechanical properties of reinforced thermoplastics depend on such characteristics of the filler as granulometry, orientation and dispersion. These different microtextural parameters were determined by using a single tool: image analysis, which was coupled with optical and electron microscopies. The different materials tested were based on short-glass-fibre-reinforced polypropylene obtained by extrusion and injection steps. For the different samples analyzed, the processing conditions and the filler concentration were constant, and variability was due to the different average lengths of the filler incorporated in the matrix. The different filler parameters were determined with particular emphasis on the techniques of dispersion characterization. The techniques developed in this study were based on image analysis. They enabled us to estimate filler-size distribution and development of the three-dimensional orientation inside the material and between different samples. The development of the filler dispersion was also made apparent. In addition, the relationships obtained between the different microtextural parameters were investigated. The general conclusion is that image analysis is very suitable for characterization of this kind of material.