By means of RT-PCR and specific primers the expression of SAP1-6 and SAP8 was investigated with respect to the time course in an in vitro candidosis model based on reconstituted human mucosal epithelium. Corresponding morphological alterations of the epithelium were documented by light microscopy. The detection of Sap was performed immunoelectron microscopically using a monoclonal antibody. In the oral candidosis model SAP1 and SAP3 transcripts were detected 42 h after inoculation corresponding to first histopathological changes. Additional SAP6 expression was observed six hours later concomitantly with germ-tube formation. Later on SAP2 and SAP8 transcripts were found after 60 h. On protein level it was possible to demonstrate Sap antigens within Candida and markedly deteriorated epithelial cells. Initial experiments with proteinase mutants and proteinase inhibitors showed reduction of histological damage. In a clinical specimen obtained from a twenty nine-year-old female patient suffering from acute oral candidosis SAP1, 3 and 6 could be demonstrated corresponding to the findings in vitro after 48 h. Investigating a clinical specimen obtained from a lesion of chronic oral candidosis in an HIV-infected patient also showed SAP2 expression. On the basis of our results a relationship between the expression on of particular SAP genes and the turn up of lesions looks as probable as a relevant contribution to the in vivo infection.