Saliva is a biological fluid that is easily obtainable and that can give useful information both in systemic and oral diseases. In this study, a chromatographic method was applied to determine the amount of defensin HNP-1 in human saliva of patients with oral mucosal diseases before and after treatments and compared with controls. Defensin human neutrophil peptide-1 (HNP-1) was identified and confirmed. The concentration of HNP-1 in saliva was determined by comparing the area of eluted HNP-1 with that of HNP-1 standard. Linear calibration range of defensin HNP-1 was 0.10 to 0.90 mu g/10 mu L with R(2) values of 0.996. The concentrations of HNP-1 in the saliva of patients with oral lichen planus, Behcet's disease, and recurrent apthous stomatitis were 33.6 +/- 10.6, 15.5 +/- 7.6, and 36.3 +/- 9.5 mu gmL(-1) (mean +/- S.D.), respectively. The salivary defensin-1 concentration was significantly higher in patients with oral mucosal diseases than in healthy volunteers; furthermore, in patients with oral mucosal diseases, the concentration was significantly higher before treatment than after treatment.