PT-01, a controlled-release insert, was developed for topical chemotherapy in periodontal disease. It is a soluble insert that consists of fast-release and sustained-release parts containing ofloxacin (OFLX) as an antibacterial agent. In this study, the release profile of OFLX from PT-01 was investigated in vitro. Twelve adult volunteers were administered OFLX as PT-01 or as an aqueous solution into their periodontal pockets, OFLX concentrations in gingival crevicular fluid (GCF) were evaluated from the viewpoint of pharmacokinetics. The in vitro release profile of OFLX from PT-01 showed a biphasic pattern. The release rate of OFLX was relatively rapid in the early phase and slow thereafter. When OFLX aqueous solution was administered into periodontal pockets, the OFLX level in GCF rapidly decreased to be about 1/100 after 30 minutes. When PT-01 was inserted into the pockets, the OFLX level in GCF immediately reached a peak (about 12 mg/ml), and gradually decreased until the 3rd day, and maintained a constant level above 2 micrograms/ml, the effective minimum antibacterial concentration for periodontopathic microorganisms, from the 3rd to 7th day after insertion. No side-effects were observed in the volunteers who received the PT-01 insert. The above results suggest that PT-01 is a suitable pharmaceutical preparation for periodontal chemotherapy.