Purpose: This cluster randomised controlled trial evaluated the effectiveness of a school-based xylitol chewing-gum programme on caries prevention among students with visual or hearing impairment. Materials and Methods: The study compared xylitol gum plus oral health education (intervention group, n = 93) with oral health education alone (control group, n = 81) among students aged 7-18 years in special needs schools in Khon Kaen, Thailand. The primary outcome was caries onset rate measured as the change in caries onset on tooth surfaces. The secondary outcome was plaque index. Between-group differences were determined using generalised estimated equations and a general linear model under the intention-to-treat approach. Results: After 1 year, there was a significantly lower caries rate in the primary dentition among the intervention group compared to the control group (0.08 vs 0.12 surfaces per surface-year, respectively; adjusted relative risk = 0.64, 95% confidence interval 0.44-0.96; p = 0.03), but there was no significant difference in the caries rates for the permanent dentition. Remineralisation also occurred more in the intervention vs the control group in the primary dentition only. Oral hygiene was significantly improved in the intervention but not in the control group (p = 0.001). Conclusion: This programme reduced the caries rate and enhanced remineralisation in primary dentition, and improved oral hygiene in students with disabilities. Keywords: chewing gum, dental caries, disabilities, randomised controlled trial, xylitol