The purpose of this study was to determine diffusion of hydroxyl ions through dentine from different calcium hydroxide [Ca(OH)(2)] medicaments. Forty-five single-rooted teeth were instrumented and cavities (3 mm in diameter and 1 mm in depth) were prepared on the facial surface of each root. After smear layer was removed with 17% EDTA all surfaces of roots, except cavities, were coated with nail polish. Teeth were randomly divided into four experimental groups ( each 10 samples) and a control group ( five samples). They were filled with: group 1, Ca(OH)(2) and distilled water mixture; group 2, TempCanal; group 3, Calasept; and group 4, Ca(OH)(2) plus point. Control group, in which nothing was applied to the canals. All samples were immersed in distilled water maintained at 37 degreesC. pH values were measured at 1 h, 2 h, 3 h, 24 h, 48 h, 72 h, 4 days, 5 days, 6 days, 7 days and 14 days. Ca(OH)(2)-distilled water mixture and TempCanal showed highest pH values at 24 h. Calasept, Ca(OH)(2) plus point and control showed highest pH values at 3 h. Time intervals after 24 h, Ca(OH)(2)-distilled water mixture, TempCanal and Calasept showed higher pH values than Ca(OH)(2) plus point, with a statistically significant difference ( P < 0.05). The pH value of Ca(OH)(2) plus point was lower than the values of other materials after 3 h. This study indicates that non-setting Ca(OH)(2) based materials have an effective release of hydroxyl ions compared with Ca(OH)(2) plus point.