With use of the half-mouth technique, a pit and fissure sealant was applied to the permanent first molars of 200 children between 6 and 8 years of age in a community with fluoridated water in Colombia, South America. Complete retention of sealant at 12, 24, and 36 months after application was 91.6%, 88.9%, and 87.5%, respectively. Partial retention of sealant was 5.8%, 7.1%, and 8.5% at the same intervals. The incidence of caries in all sealant-treated teeth at 36 months was 8% vs 53% in untreated paired teeth. Of the 238 teeth that completely retained sealant, only one tooth had occlusal caries at 36 months. No statistically significant difference in complete retention between maxillary and mandibular molars was noticed at any examination. The study confirms that this cold-cured pit and fissure sealant is effective in protecting the occlusal surfaces of teeth against caries for at least three years.