Background: Chlorhexidine (CHx) mouthrinse was the first choice for gingivitis. The loss of taste and tooth discolorisation was motivated the clinician to dilute CHx 0.2% to 1:1. Aims: To compare the effectiveness of CHx 0.2% and diluted CHx 1:1 as mouthrinse on gingivitis and evaluate tooth discoloration. Method: Ninety nine students with mild and moderate gingivitis at SMU Labs School jakarta age between 14-15 years had participated. The subjects were randomised selected and double-blind method was applied. The subjects were divided into 3 groups. The first group was instructed to rinse with CHx 0.2%, the second group rinsed with diluted CHx 1:1, and the third group as a control without rinsing. The first and the second groups were rinsing the regimen for one minute, twice a day in 7 days, in the morning and night. Plaque and bleeding were scored using Plaque Index (Loe and Silness), and modified Papilla Bleeding Index (Muhleman) on the first and seventh day of the study. The changes of scores (PII and PBI) before and after rinsing were analyzed using "paired t test". The differences of the effectivity of CHx 0.2%. CHx 1:1 and control groups using "ANOVA test" with 95% probability. Differences of tooth discolouration after rinsing were analyzed by "independen t test". Probabilities of less than 5 percents were taken to be statistically significant. Result: The results showed at day 7, not significant difference between CHx groups for plaque (CHx: 0.74, CHx 1:1: 0.66), and gingival bleeding (CHx: 1.02, CHx 1:1: 0.83). The proportion of tooth discolouration was not significant in the diluted CHx group (4.8%) and in the CHx group (7.3%). Conclusion: Diluted CHx 1:1 effectively on gingivitis. The clinician can be used in the clinic whereas the lost the taste were reduced. No differences significant of tooth discolourisation between rinsing regimens on seventh days.