Lidocaine has been widely investigated as a local anaesthetic and cardiac antiarrhythmic agent. Articaine is the mostly used local anaesthetic agent in German dentistry. Blood levels of local anaesthetic agents after application in dentistry have been measured only in peripheral venous blood. Concentrations in the target region near the pain receptor have not been investigated. Therefore it seemed worth to compare the concentration of lidocaine and articaine in the upper and the lower jaw after extraction of a tooth as well as the penetration and distribution of the drug in the tissue and bone of the jaw. For this purpose a method for withdrawing blood from the alveolus after extraction of a tooth was developed. First patients were submitted to submucous injections of lidocaine (2.3 ml 2%) into the upper jaw and to mandibular block injection of lidocaine (2.0 ml 2%) into the lower jaw. Correlation between blood levels of lidocaine and the type of anaesthesia as well as the location of the extracted teeth were found. In the upper jaw very high concentrations of both anaesthetics were found and the blood levels of lidocaine in the region of incisors were higher compared to those in the region of molars. In the lower jaw the blood levels of lidocaine were on average ten times lower than in the upper jaw and the highest values were found in the region of molars. Secondly, blood samples were withdrawn from the alveolus of the upper molars 3 to 23 min after submucous injection of articaine (2.0 ml 4%) or identical injection of lidocaine (2.0 ml 2%).(ABSTRACT TRUNCATED AT 250 WORDS)