To monitor the level of soil acidification in the county of Varmland in the middle west of Sweden 180 podzolic forest soils were investigated. Soil solutions from four horizons were obtained by centrifugation and the soil was sampled for a determination of the exchangeable pool by extraction. The concentrations of inorganic Al and its fraction of the total Al in solution were greater in the south of the county (up to 50%). The factors influencing the total Al and free inorganic Al 3 + in the soil solutions were evaluated. Saturation indices (SI) for five different mineral phases were calculated but none implied equilibrium conditions. The relationships between pAl 3 + and pH (in the pH range 4-6.2) gave slopes of about 1, which indicated that ion exchange/complexation reactions may be important for determining the Al 3 + concentration in the B and C horizons. In the E horizon solutions complexation with soluble organic acids seemed to be the major factor which influenced the Al 3 + activity. The influence of organic matter on Al solubility was supported by partial least square (PLS) regressions.