The results of a study on Zn, Cu, Ca and Mg content in whole saliva and supernatant of young adults in relation to caries prevalence are reported. A total of 225 university students were selected for the study on the basis of voluntary participation. The salivary electrolytes showed a high intersubjective variability and females had significantly lower levels than males. In whole saliva, the trace elements were highly correlated, whereas the correlations were weaker in the supernatant. The ratio supernatant/whole saliva varied between subjects and according to the examined electrolytes. No association could be found between the measured trace elements and DMFT. When we analysed the relation with recent caries experience in the subgroup of subjects undergoing oral examinations for at least 1 year, we found evidence that the Zn/Cu molar ratios in whole saliva were significantly decreased in subjects with more than three decayed teeth compared with those with no caries (1.54 vs. 1.11, P < 0.05). No significant association was found when supernatant was analysed. We conclude that the electrolytes' levels in whole saliva might be more adequate than the levels in supernatant to evaluate the relationship with caries.