For patients aged 5 to 9 and 11 to 14, 100 occlusal surfaces on newly erupting permanent molars were treated with a self-curing pit and fissure sealant. All teeth were categorized according to stage of eruption and sealant thickness of the coating applied. After 36 months, 75 surfaces were examined for a final evaluation; 52 surfaces (70%) did not need retreatment. Of the 23 surfaces retreated as a result of sealant loss or marginal deterioration, 18 were retreated only once in the six recall evaluations. Those molars treated originally with the operculum covering the distal marginal ridge of the occlusal surface had twice the probability for retreatment as teeth not treated until the entire marginal ridge was exposed. The thickness of the sealant coating did not affect the early signs of sealant failure.