To assess the relationship between the care index and the mean dmft/DMFT in different populations of 5-, 12- and 14-year old children.Information from recent studies of 5-, 12- and 14-year old children, co-ordinated by the British Association for the Study of Community Dentistry (BASCD) was used. The correlation between the mean dmft/DMFT and the care index for each health district was calculated for each age group, along with the linear regression equation of the care index in terms of dmft/DMFT.All the correlation coefficients were negative indicating that the care index would be expected to increase as the disease levels decrease. For the 5-year-old children in 1995/96 three other factors for the same time period; dentist:population ratio, percent of children registered and standardised mortality ratio (SMR), were also included in the model. This did not change the negative relationship between dmft and the care index.The strong negative relationship between the care index and mean dmft/DMFT levels indicated that in a situation where disease levels are reducing over time, the care index would be expected to increase. Conversely in a situation where disease levels were increasing the care index would be expected to fall.