Comparatively few studies have evaluated the distribution of drugs into human dental pulps of teeth with closed apices after oral administration . The objective of this study was to investigate whether or not tetracycline is distributed into dental pulp after oral administration. In the experimental group, patients were instructed to take tetracycline 500 mg after meals three times a day for two days prior to tooth extraction. Each extracted tooth was immediately sectioned and examined under ultraviolet light for the presence or absence of yellow fluorescence. Yellow fluorescence was found in all teeth in the experimental group. This was absent in the control teeth. It was also found in blood vessels of pulp chambers and root canals, and predentin lining the root canals. It is concluded that drug goes into human dental pulp of teeth with cloesd and opened apices after oral administration