Introduction. Metronidazole is the drug of choice in the treatment of periodontal pockets up to 5 mm in depth. It is topically applied - directly into the periodontal pockets. There are no registred trademark preparations for this purpose in the market of Serbia and Montenegro. The aim of our latest research was to test the efficacy of newly formulated preparation containing 25% metronidazole suspended in a lipogel in vitro - in anaerobic cultures isolated from the periodontal pockets, and in vivo - by the direct application into periodontal pockets. Methods. Preparation efficacy was tested in a randomized controlled study involving 25 patients, and was confirmed by the membrane-free agar diffusion method on the anaerobic strains isolated from the periodontal pockets. The duration of the testing was 30 days. The preparation was applied twice - immediately after the taking of the first swab, and on day 15, when the control swab was taken for the assessment of the effects of the applied preparation. Results. Seven anaerobic strains were isolated and tested, and each was confirmed as highly susceptible to metronidazole. Anaerobic strains were not isolated in any of the pockets treated with metronidazole-containing lipogel. The strains isolated in the control pockets were the same as were those at the beginning of the study. Conclusion. Metronidazole, in a lipogel-type base applied in the concentration of 25%, provided an efficient treatment of anaerobic infection in the periodontal pockets.