Antiseptic activity of five mouthrinses containing 0.10%, 0.12% and 0.20% chlorhexidine, as well as aqueous chlorhexidine solutions at the same concentrations were determined under usual conditions (advocated dilutions by the manufacturers and short contact time) and according to French Pharmacopoeia recommendations. The three aqueous solutions and two mouthrinses containing 0.12% chlorhexidine were not antiseptic according to the fixed criteria. Bactericidal activities of the different dilutions of products were tested with an appropriate micromethod against nine-bacterial species involved in periodontal disease. Efficacity of mouthrinses were variable and were not agreed with the aqueous chlorhexidine-corresponding solutions: the mouthrinse containing 0.10% chlorhexidine reached 0.20% aqueous solution efficacy, and the mouthrinses containing 0.12% chlorhexidine were generally less active than the 0.12% aqueous chlorhexidine solution. Therefore, antibacterial activity of this type of product cannot be anticipated with the sole concentration factor, excipients playing essential part in the chlorhexidine activity.