Blind photographic assessments were made of the permanent incisors of 322 children who had participated in two successful fluoride drop/tablet hygienist-based preventive dentistry programmes. Two groups of four dental and two lay assessors unanimously scored 57% of dentitions as mottling-free. The dental observers unanimously scored 37 children (12%) with some symmetrical homologous tooth-type mottling, although only 13 decisions (4%) were scored "unacceptable easthetically". The lay assessors rated 77 children (24%) with mottling, 15% being easthetically displeasing. However, no significant mottling differences were noted between cohorts which had commenced oral fluoride supplementation at birth and those which either commenced as late as 7 years of age, or which had never taken any such supplementation. Thus other fluoride sources must have been responsible for the non-drop/tablet diffuse symmetrical mottling noted, the most likely being highly fluoridated dentifrices ingested by youngsters unable to control the volume dispensed and swallowed. Hence the evidence does not suggest that this proven caries-inhibiting F- drop/tablet regime dosage should be reduced. There is, however, a clear and continuing need for both the dental profession and the public to be made more aware of the problem of uncontrolled fluoride ingestion from other sources.