The solution Al and exchangeable Al extracted by 0.01 M CaCl2and 1 M KCl, respectively, from the acidic soils of Trinidad were characterized for the hydrolysis products of aluminum ions. The aluminum hydroxide ion product, pAl(OH)3, was found to be independent of solution pH (≥4.0 ≤6.3) when Al(OH)2+, Al(OH)2+, Ale(OH)153+or possibly some other polymer species, and neutral species Al(OH)30were considered as the hydrolysis products. The monomer species Al(OH)2+and Al(OH)2+, and the polymer species, Al6(OH)153+were present in small amounts. The pAl(OH)3values were 34.86 ± 0.16 and 34.77 ± 0.19 for solution Al and exchangeable Al, respectively.The fraction of the total Al present in each hydrolysis species as a function of solution pH was presented graphically. It was found that the predominant species up to pH 4.5 was Al3+, and from pH 4.5 to 6.3 it was the neutral aluminum species Al(OH)30.