AbstractThe aim of the present study was to examine yearly increments in exposure, cumulative exposure, and mean proportion of lifetime exposure to optimally fluoridated water supplies of Australian adolescents over the period 1960 to 1978 and to conditionally predict trends in those exposure measures from 1979 to 1990. The basis of the study was the history of the introduction of water fluoridation. Yearly increments were found to have been most varied, but cumulative exposure has continued to increase from a negligible level in 1960 to approximately two‐thirds of adolescents being exposed in 1978. Proportion of lifetime exposure was represented by a smooth sigmoidal curve with time‐lagging of successive curves for higher ages between 12 and 17‐yr‐old. Proportion of lifetime exposure was predicted to increase through to 1990 and 1996 for 12‐and 17‐yr‐olds, respectively. This prediction showed little sensitivity to yearly increment conditions from