The clinical characteristics of 24 active root surface lesions on buccal surfaces were recorded through 18 months after implementation of meticulous toothbrushing with a fluoride toothpaste (F congruent to 0.1%). Within a period of 2-6 months all lesions had changed from soft, greasy and yellowish to leathery or hard, darkly discoloured tissue, indicating a gradual transition from active into inactive stages of caries. The observations stress the dynamic nature of the root caries process. It is concluded that when dealing with root surface caries it is essential to distinguish between active and inactive lesions and that classical operative treatment to a great extent can be avoided.