The fluoridating efficiencies of five fluoridated toothpastes have previously been studied in an in vivo model. The aim of this study was to correlate fluoride uptake in partially demineralized enamel with the volume of toothpaste used. The amounts of free ionic fluoride, fluoride as MFP and total fluoride delivered by the toothpastes were evaluated and correlated with the observed fluoride uptake in the enamel. Substantial differences between participants were discovered in the volumes of toothpaste used. However, for any given participant a relatively small variation was found in the amount of toothpaste used between the various pastes tested. A positive correlation was found between the amount of toothpaste used and the corresponding fluoride uptake. Furthermore, the levels of free ionic fluoride and MFP in the toothpastes linearly correlated with the fluoride uptake. On the other hand no such correlation was observed for the amount of total fluoride.