The aim of this study was to examine whether brownish crown and root discoloration of wisdom teeth was related to treatment of acne with tetracyclines. For this purpose, 17 discolored third molars from nine patients were embedded without being decalcified, ground along the tooth axis, and examined using fluorescence microscopy. A thorough medical history served to determine the start and duration of any administration of tetracyclines. This confirmed the use of drugs against acne containing minocycline in all cases except one. The microscopic analyses of all teeth revealed intensely fluorescent bands in the dentin, which corresponded to the mineralization front at the time of tetracycline intake. More or less uniform discoloration of the entire crown was seen in association with treatment against acne prior to the completion of crown formation at the age of about 15 years. This uniform staining can be attributed to incorporation of minerals during ongoing maturation of the occlusal enamel, which is concomitant with the formation of the cervical crown regions. When acne was treated between 15 and 22 years of age, only the roots of the third molars displayed annular discolorations, which seemed to result from the incorporation of tetracyclines into dentin, while fine fluorescent incremental lines in root cementum were too thin to be apparent clinically. Three accidentally removed interradicular bony septa revealed that tetracyclines incorporated into alveolar bone remained there for about 2 years, but thereafter disappeared as a result of physiological remodelling.