Dioctahedral smectites (Cheto- and Wyoming-type montmorillonites and a beidellite) were treated with two hydrolysed OH-Al solutions (0.02 m in Al) containing different OH-Al complexes. The ratio of ~3.25 mmol of Al per gram of smectite was used. The total Al and the presence of OH-Al species in solution before and after reaction with smectites were determined by the kinetics of Al-Ferron reaction colour development. The composition of the Al species retained by smectites was not the same as that present in the original solution added. The slow-reacting complexes present in the solution were preferentially adsorbed by dioctahedral smectites. Smectites prepared from slow-reacting polymer solutions showed changes in interlayer separation, b-dimension, order along the c axis and spectroscopic properties, after storage at room temperature. The OH-Al Cheto-type montmorillonite prepared from both solutions showed more retention of Al, best stability at room temperature and after thermal treatment at 550°C than interlayered OH-Al Wyoming-type montmorillonite and OH-Al beidellite smectites.