The objective was to determine the percentage contribution of parotid saliva to whole saliva and to the saliva at 11 sites in the mouth, when flow rate was unstimulated or stimulated with chewing-gum. The marker substance used was alpha-amylase, as this is in much higher concentration in parotid saliva than in secretions from other salivary glands. Formulae were derived for calculation of the minimum, maximum, and mean percentage contributions of parotid saliva to saliva in different areas of the mouth. The results, from 10 individuals, showed that the contributions of parotid to unstimulated and stimulated whole saliva averaged 30.1% and 35.6%, respectively, whereas the corresponding values for samples from the region vestibular to the upper molars were 56.1% and 61.4%, but only 2.8% and 6.8% for samples from an area vestibular to the upper incisors. Thus parotid saliva was not evenly distributed throughout the mouth. Stimulated samples mostly contained significantly higher proportions of parotid saliva, but the distribution of the parotid saliva was still extremely variable. Because the different regions of the mouth are not exposed to the same fluid environment, this may influence the site-specificity of supragingival calculus deposition and of various diseases such as dental caries.