It is well known that the spatial distribution and the spatial density of the particles of alpha-AlFeSi and beta-AlFeSi in the billets of Al-Mg-Si alloys, such as AA6063 alloys affect the quality of anodizing performance of their extrusions. For this reason it is very important to control the spatial distribution and the spatial density of both AlFeSi particles at extrusion plants. The X-ray diffraction method (XRD) has been used for discrimination between alpha-AlFeSi and beta-ALFeSi particles. However it is not an appropriate method for determining the spatial distributions of particles in the alloys. As an alternative method an electron probe microanalyzer (EPMA) has been used for determining the spatial distributions of each element in the microstructures. However, unfortunately it is difficult to discriminate between the particles composed of the same elements like alpha-AlFeSi and beta-AlFeSi particles. Thus, we tried to develop a convenient method to discriminate between alpha-AlFeSi and beta-AlFeSi particles in the microstructure of AA6063 alloys and developed the EPMA mapping of alpha-AlFeSi and beta-AlFeSi particles. First, in order to discriminate between the two particles, we tried to use the relative X-ray intensity ratio, the I-Fe/I-Si ratio instead of the Fe/Si mass ratio. Then, we calculated the value of the I-Fe/I-Si ratio from alpha-AlFeSi and beta-AlFeSi by using Monte Carlo calculations and obtained the critical value of the I-Fe/I-Si ratio, to distinguish between alpha-AlFeSi and beta-AlFeSi. After that, using the discrimination value, we developed the EPMA mapping program ( EPMA method) to observe the distributions of alpha-AlFeSi and beta-AlFeSi, and to calculate the areas (%) of alpha-AlFeSi and beta-AlFeSi. Finally, we checked the correlation between the EPMA and the XRD methods. Consequently, the two methods were in good agreement. Today, this EPMA method instead of the XRD method is successfully used in the quality control of 6063 aluminum alloy billets after heat treatment at our aluminum extrusion works. (C) 2003 Kluwer Academic Publishers.