BACKGROUND This study aims to define the influence of chlorhexidine on taste, considering either its concentration in mouthwashes or time of rinsing. METHODS Suprathreshold taste acuity of 40 healthy subjects tasting variously concentrated solutions of sucrose, sodium chloride, citric acid and quinine hydrochloride was determined. Subjects were divided into four groups. Three groups rinsed their mouths during one minute, twice a day, for seven days, with a selected mouthwash (respectively 0.12%, 0.20%, and 0.30% chlorhexidine solutions). The fourth group rinsed in the same manner with a 0.30% chlorhexidine mouthwash, and time of rinsing was 15". RESULTS All the mouthwashes reduced taste acuity for salt and bitter; the perception of sweet and sour was not significantly modified. Chlorhexidine acted on taste in different ways: salt perception reached the lowest value on the second day of treatment and the degree of hypogeusia changed no more till mouthrinses were interrupted. Bitter perception was progressively reduced and reached the lowest value on the seventh day. In both cases taste reduction lasted some days after the interruption of mouthrinses. Quality of all tastes was altered by mouthwashes, but incidence of dysgeusia was not related to chlorhexidine concentration. CONCLUSIONS Hypogeusia induced by chlorhexidine concerns specifically salt and bitter. Chlorhexidine concentration in mouthwashes till 0.12% and mucosa exposure not exceeding 60" twice a day, seem the best procedure to protect tastes in clinical practice.