Summary.The author's micro method for the determination of pH in saliva (SCHMIDT‐NIELSEN, 1945) is applied. It is found that:1) Resting saliva can only be obtained when the person studied is sitting completely quiet. Even talking, mastication, coughing or anything like that causes a marked increase in the pH of saliva.2) The pH of resting parotid saliva is remarkabley constant for the single person, not only during 24 hours, but also from day to day and from month to month. The pH of mandibular saliva does not show quite the same constancy, this is perhaps partly due to the technique employed.3) The pH's of parotid saliva from 40 persons range from 5.45 to 6.06 (average 5.81). The pH's of mandibular salliva range from 6.02 to 7.14 (average 6.39).4) Stimulation causes a considerable rise (up to two pH units) in the pH of the saliva. Gustatory, olfactory and mechanical stimuli were tried. Gustatory stimuli were found to have the strongest effect up