Objective: To investigate the effects of fluoride toothpaste on acid-etched enamel by means of a scanning electron microscope. Methods: Permanent first premolars extracted for orthodontic reasons were etched with 37% H3PO4. They were divided into two groups in pairs of contralateral teeth. Group 1 was treated with fluoride toothpaste slurry; Group 2 was treated with deionized water. Treatment time was three weeks (one hour, 3 times a day). Results: At the conclusion of the experiment, large amounts of precipitate were observed on the enamel surface of the teeth that were treated with fluoride toothpaste slurry. The etched structures were no longer evident and the enamel surface was smooth. The acid resistance of the teeth was significantly enhanced. However, clearly etched enamel structures were visible on the enamel surface of the teeth that were treatd with deionized water. Conclusion: Fluoride toothpaste could promote the remineralization of etched enamel and enhance its resistance to acid attack (CJDR 1999;2(3)79-83)