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Forty-six deciduous teeth from caries-free children who had been exposed to systemic fluoride tablet treatment (0.5–1 mg F^––/day) from 3 months prenatally to 7 years of age were examined histologically and chemically. In addition to the systemic fluoride exposure the children were treated every 4 weeks with fluoride gels after 5 years of age. Twenty-two teeth from children born and reared in an area with less than 0.2 ppm fluoride and never exposed to tablets and gels acted as controls. All teeth in the fluoride group exhibited distinct subsurface hypomineralized lesions along the entire enamel surface. In addition, most of the molars showed a very thick well-mineralized outer enamel in the occlusal half of the crowns. The fluoride distribution pattern within the enamel was similar in both groups, but substantially higher in the outer enamel in the fluoride group. Thus, at 100 μm depth the fluoride concentration was > 1,000 ppm in the fluoride group as compared to < 200 ppm in the control group. The structural and chemical findings showed that the tablet regime was capable of producing fluorotic lesions which may have been modified in molar teeth by the gel treatments. It is suggested that these observations should be taken into account when considering doses to be recommended for fluoride preventive programmes.