H-smectites, with protons covering over 80 % of cation exchange capacity (CEC), were prepared from Jelsovy Potok (Slovakia), Upton (Wyoming, USA) and Horni Dunajovice (Czech Republic) montmorillonites, and SWa-1 ferruginous smectite (Grant County, Washington, USA) using H-OH-H resin columns. The number of strong acid sites decreased and the number of the weak ones increased in course of aging of H-smectites in suspension. Iron was released in the process of autotransformation into the exchangeable positions of H-montmorillonites similarly to aluminium and magnesium. Increased amounts of exchangeable Mg, Al and Fe were found after repeated passage of the H-smectite through the resins. Highest relative amounts of Mg were found in all fresh H-smectites, however, in montmorillonites higher proportions of Al and Fe than of Mg were released in course of aging. The order of relative amounts of cations in exchangeable positions Mg>Al>Fe was not changed in course of aging of ferruginous smectite.