In this study, the capacity of contingency tables and correspondence analysis (CA) to determine graphically what categories of edaphic variables vary with Site Index (SI) is analysed. The categories that show association with SI are those related to textural type and water holding capacity. Furthermore, 66 discriminant rules are tested for their ability to classify plots into SI classes using edaphic data. A discriminant rule for classifying observations into two SI classes according to elevation and soil texture (represented by the silt and clay content) is presented for stone pine (Pinus pinea L.). This model was chosen based on a cross-validation. The error rate was 29.4% for the best quality group and 21.7% for the lowest quality group. © INRA, EDP Sciences, 2005.