Influence of the type and amount of acid, used for aluminium hydroxide peptization, on the crystallinity and specific surface area of the dispersed phase of boehmite sols as well as the pH of sols, was investigated. The ratio n(HCl)/n(Al(OH)(3))=0.1 was found to be optimum for aluminium hydroxide peptization. Higher acid to aluminium hydroxide ratio leads to a decrease in specific surface area and crystallinity of the solid phase as well as in pH of sols. Increase in counter ion (Cl-) concentration causes a shift in d values of (020) crystallographic plane, from the value corresponding to boehmite to that for pseudoboehmite, and a decrease in specific surface area of the sol solid phase. Using HNO3 as a peptizing agent, greater crystallinity and higher specific surface area values of the solids were registered. (C) 2003 Elsevier B.V. All rights reserved.