In this investigation, we report a method of periodontal pocket disinfection by local exposure to ultraviolet radiation in the periodontitis treatment. We surveyed 25 patients with chronic generalized periodontitis diagnosis in severe and moderate severity, namely 10 patients in the main group and 15 patients in the control one. In the complex treatment, we exposed the periodontal pockets to ultraviolet in situ by means of newly developed optical system. The investigation revealed positive clinical and microbiological results.