The authors report on the effectiveness of a school-based, supervised toothbrushing program among a group of 112 children with Down syndrome in Kuwait. The study involved 45 boys and 67 girls, who ranged in age from 11-22 years (mean, 14.8 years). The participants had moderate mental retardation and attended one of two special needs schools. Plaque was scored according to the Silness and Löe plaque index and gingivitis according to the Löe and Silness gingival index. Supervised toothbrushing and dental health education sessions were conducted twice a week. The program was evaluated at the end of three months. The mean plaque score decreased from 1.93 to 0.95 (p < 0.001), and the mean gingival score from 2.00 to 0.83 (p < 0.001). This three-month supervised toothbrushing program was effective in reducing plaque and gingivitis scores, but the key to long-term success of the program is sustaining the children's motivation to make oral hygiene a part of their daily life.