The effect of aluminum complexation on the net decomposition rate of purified humic acid (HA) and fulvic acid (PA), extracted from a podzol B horizon in the Netherlands, were studied at room temperature (20°C). Net decomposition rates were determined from CO₂ evolution from samples as measured by gas chromatography. Increasing aluminum additions significantly reduced the decomposition rate of HA, of PA, and of organic matter in podzol B horizons, whereas pH had no notable effect on decomposition rates. Results indicate that at the current high depletion rates of organically-bound soil Al, due to acid rain, the decomposition of soil humic compounds may increase significantly . This may have serious consequences for the ecologically relevant pool of humic compounds in forest soils.