Abstract A 3-month study was conducted to determine the effect of a 10 per cent urea peroxide solution on gingivitis and oral debris accumulation in orthodontic patients. Sixty fullybanded children (thirty-two girls, twenty-eight boys) 10 to 17 years of age were randomly placed into two groups of thirty members. The treatment group was assigned the use of the test solution and given normal oral hygiene instructions. The control group was given only the normal oral hygiene instructions. The subjects' gingival status was evaluated by means of the gingival index (GI) of O'Leary. The accumulation of oral debris was monitored by means of the oral debris index (ODI) of Greene and Vermillion as modified by Womack. Subjects were scored at the start of the study and approximately 1 and 3 months thereafter. Analysis of variance of the GI and ODI scores revealed significant treatment effects (p = 0.0013 and p = 0.0051, respectively), which substantiated the clinical observations. Rinsing with the test solution in conjunction with toothbrushing appears useful as an oral hygiene measure for orthodontic patients. No adverse reactions were experienced by any of the patients using the test solutions.