A new method for treating carious dentine with alpha-tricalcium phosphate (alpha-TCP) dental cement containing antimicrobial agents has been recently introduced. However, the release behavior of antimicrobial agents from this cement has not yet been clarified. The aim of this study is therefore to examine the release profile of the antimicrobial agents from the alpha-TCP cement. Three kinds of antimicrobial agents (metronidazole, cefaclor and ciprofloxacin) were added to two commercially available alpha-TCP cements (new apatite liner type I and type II). The set cements were then immersed in water at 37 degrees C and the released antimicrobial agents and Ca ion were determined at regular intervals for three months. In addition, scanning electron microscopic observations were conducted before and after immersion for three months. The release profile of the cements containing antimicrobial agents varied depending on the types of antimicrobial agents. The incorporation of antimicrobial agents affected the setting reaction of the cements. The release behavior of the drugs also varied depending on the types of the cements. The differences in the release profile between type I and type II cements reflected the structures and compositions of their matrices.