Three clinical trials were carried out to evaluate the effects of mouthrinses containing 5n-octanoyl-3'-trifluormethylsalicylanilide (salifluor) on plaque and gingivitis. Each trial was performed as a double-blind, randomised and cross-over designed study (studies 1, 2 and 3). In each study, 10 young individuals with healthy gingiva abolished all means of mechanical plaque control during the course of the experimental period including 6 x 4 days (study 1), 3 x 18 days (study 2) and 3 x 14 days (study 3). They rinsed, 2 x daily, with various mouthwash preparations for 4 days (study 1), for the last 4 days of a 18 day period (study 2) or for 14 days (study 3). 6 (control, vehicle control, 0.08%, 0.12% and 0.2% salifluor and 0.12% chlorhexidine), 3 (control, 0.12% salifluor and 0.12% chlorhexidine) and 3 (control, 0.12% salifluor and 0.12% chlorhexidine) mouthwash preparations were tested in studies 1, 2 and 3, respectively. The findings of study 1 indicated that (i) mouthrinses containing salifluor were significantly more effective than control rinses and that (ii) the salifluor mouthrinses were equally effective as the 0.12% chlorhexidine mouthrinse, in retarding 4-day de novo plaque formation. The findings of study 2 indicated that (i) the mouthrinse containing 0.12% salifluor retarded de novo plaque formation to the same extent as the 0.12% chlorhexidine mouthrinse at healthy as well as at inflamed sites but that (ii) the anti-plaque effects of the salifluor and chlorhexidine mouthrinses were significantly smaller at sites with inflamed than with healthy gingiva. In study 3, it was observed that there was no significant difference between the 0.12% salifluor and 0.12% chlorhexidine mouthrinses in retarding de novo plaque formation and the development of gingivitis during a 14-day period of no mechanical plaque control. Thus, the results of the 3 clinical trials demonstrated the potential of salifluor as an effective anti-plaque and anti-inflammatory agent.