Fluoride concentrations were determined in saliva from children and young adults by means of a fluoride ion electrode (Orion Research Inc.). Children who consumed drinking water containing 1 ppm fluoride (Group 1) showed a mean fluoride concentration of 0.009 ppm in parotid saliva. Children residing in a community with less than 0.1 ppm fluoride in the drinking water (Group 2) showed a mean concentration of 0.007 ppm. The comparable mean concentration was 0.008 ppm in children from the same community receiving a daily supplement of 1 mg fluoride (Group 3) while adults from a non-fluoridated community who refrained from the use of fluoride dentifrices for one week (Group 4) had a mean concentration of 0.010 ppm in parotid saliva. It was further found that simultaneously collected stimulated parotid and submaxillary saliva had identical concentrations on an individual basis. Fluoride concentrations were higher in whole saliva than in duct saliva from the same individual. The mean fluoride concentration in whole saliva in Group 1 was 0.033 ppm compared to 0.011, 0.015 and 0.017 ppm respectively in Groups 2, 3 and 4. The increased fluoride concentrations in whole saliva were attributed to inclusion of cellular debris and mucus since the concentrations decreased when whole saliva was ‘cleared’ by centrifugation. Also the fluoride concentration tended to decrease in a series of successively collected samples of whole saliva. Dental plaque and material scraped from the tongue contained significant amounts of fluor