THE PURPOSE OF THIS STUDY was to investigate the fluctuation of gingival crevicular pH during experimentally evoked gingivitis and occlusal trauma, and to examine the relationship between the pH and periodontal health status using a newly developed pH sensor Maxillary first premolars with clinically healthy gingiva were selected as test teeth in 10 volunteers. In the first study phase, experimental gingivitis was evoked, and gingival index, plaque index, and crevicular pH were recorded during the study period. In the second study phase, experimental occlusal trauma was created with metal onlays having occlusal interferences in lateral movements, and tooth mobility and pH were recorded during the study period. In the gingivitis phase, GI, PlI, and pH values fluctuated significantly during the study period (P < 0.01) and positive correlations were observed between both GI and pH values (P < 0.05), and PlI and pH values (P < 0.01). In the occlusal trauma phase, significant fluctuation was found among tooth mobilities (P < 0.05) during the study phase, but not in pH values. Statistically significant correlations were not observed between tooth mobilities and pH values. These data suggest that the crevicular pH level may not be influenced by experimental occlusal trauma, but shifts toward alkaline with experimental gingivitis.