Abstract –Objectives: The aim was to evaluate the effectiveness of a preventive oral health program on the prevalence of oral candidosis in 237 frail or dependent residents in a long-term care facility. Half of the residents were included in an experimental group which benefited from a preventive oral hygiene program including instruction of the carers and implementation of a recall program for professional oral hygiene care. Methods: Intraoral examinations and yeast cultures from the oral mucosa and the fitting denture surface were carried out at baseline and 18 months later. The outgrowth of yeast was estimated on Oricult-N dip slides using the scale: no growth; 1–20 colonies; 21–100 colonies; >100 colonies. Results: At baseline (n=237) and at 18 months (n=159) the experimental and the control groups were similar with regard to the residents' distribution by age, sex, dental and prosthetic status and prevalence of denture stomatitis. The 78 residents lost had the same baseline characteristics as the survivors, except for being older. In the experimental group the severity of the inflammation of the palate decreased (P=0.005) as well as the prevalence of glossitis (P=0.005). At baseline high yeast scores from the mucosa (>20) were observed in about 50% of the residents in the experimental as well as the control group. At 18 months this figure was 23.4% for the experimental and 48.7% for the control group (P=0.001). There was also a reduction of the number of residents with positive cultures and the denture yeast scores at 18 months in the experimental group (P=0.05). Conclusions: This study has shown that the preventive program was effective in reducing the colonization of the oral mucosa and dentures by Candida and thereby improving the health of the oral mucosa.