Salivary bacteria produce the enzyme lysine decarboxylase which converts lysine to cadaverine. In the absence of appropriate oral hygiene, overgrowth of these bacteria depletes lysine. This may contribute to gingival inflammation, while cadaverine contributes to oral malodor. A selective and sensitive capillary electrophoresis method with laser-induced fluorescence detection has been developed for the determination of cadaverine and lysine in saliva, as an indicator of lysine decarboxylase enzyme activity. The diamino compounds were separated in acidic background electrolyte in their mono-labeled form after derivatization with 4-fluoro-7-nitrobenz-2-oxa-1,3-diazole (NBD-F). Linearity and reproducibility of the method in the range 1-50 μmol L(-1) have been demonstrated using saliva samples. The method was applied for the measurement of cadaverine and lysine in the saliva of healthy volunteers with or without proper oral hygiene. In the absence of oral hygiene, the mol fraction of cadaverine to cadaverine plus lysine in saliva increased significantly (0.65 ± 0.13 vs. 0.39 ± 0.18, P < 0.001), indicating the presence of higher amount of bacterial lysine decarboxylase, that may contribute to periodontal diseases.