Objective:To investigate the effects of periodontal treatment on the levels of substance P(SP) in gingival crevicular fluid(GCF), resulting in a return to periodontal health. Method:The course of non-surgical treatment was performed in 15 patients. Clinical indexes were measured at periodontitis site before treatment and at 8 weeks after the completion of treatment in each subject. A 30-s sample of GCF was collected from each test site using perio paper strips. The volume of GCF was calculated, and the SP level was analysed by radioimmunoassay. Results:The clinical condition of all test sites improved as a result of the periodontal treatment. The levels(pg/30 s sample) of SP fell from 45.48 before treatment to 10.11 after treatment(P < 0.05). The concentration(pg/ml) of SP in GCF fell from 36.90 to 25.82(P < 0.05). Conclusion:The reduction in inflammation resulting from effective periodontal treatment was associated with a reduction of neurokinin SP in gingival crevicular fluid.