The effect of acidity on the accumulation of Al in the aquatic bryophyte Fontinalis antipyretica was studied. The main interest of this study was in characterizing the relationship between the two parameters, as Al is typically mobilized in acidic environments, where it becomes extremely toxic. With this aim, a series of laboratory experiments were carried out where samples of F. antipyretica were held in tanks of water with different concentrations of Al (0.1-3 mg L(-1)) and levels of acidity (pH 3-5. 8). The incubation time varied between 1 and 24 h. In general, the greatest accumulations of both intra- and extracellular Al were found at a pH of 4.4. With the results obtained, the kinetics of both intra- and extracellular Al uptake was characterized, and models constructed for different combinations of Al and acidity. The study was completed by examining the relationship between the pH of the holding water and bioaccumulation of Al and the variation in concentration of cations essential to plant life, which are also indicators of changes in cellular physiology (K, Mg, Ca). In general, losses of these elements were found at intra- and extracellular locations, especially at high pH.