Asker is a capital suburb where a preventive philosophy has guided the public dental health services for decades. In the period studied the child population aged 3-13 yr increased from 3208 to 6008. In the school age groups 7-15 yr practically all children in the community have participated in the dental service programs. The objective of the paper is to present retrospectively the changes in caries status of children under near optimal dental health care conditions and to expose reported preventive activities. A considerable increase in the proportion of "caries free" pre-school children occurred in the period 1976-88. A maximum was reached in the latter part of the eighties, whereafter a leveling off is suggested. For school children a rapid increase in "caries free" children took place for the lowest grades, starting before 1976. The higher grades came later and at a slower pace. The great number of fillings inserted in 1966-72, oscillating around 60 surfaces for the nine school years, decreased rapidly during the following decade and seems now to have settled around a total average of five to six surfaces. This implies a reduction of 90% in 20 yr. In most age groups these changes started before 1970. The major part of the caries decline occurred in the seventies and a leveling off is apparent during the eighties. The average number of filled surfaces per year has fallen from 6.6 in the 1955 birth cohort to 0.7 in the 1977 cohort, a reduction of 89% in 22 yr.(ABSTRACT TRUNCATED AT 250 WORDS)