Oral submucous fibrosis (OSF) is an oral precancerous condition, and is associated with betel quid (BQ) chewing habits. It is a disorder of excessive deposition of collagen in the connective tissues that results from disruption in the regulation of the equilibrium between matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs). Elevated TIMP-1 protein has been thought to be associated with oral fibrosis, however whether TIMP-1 expression in OSF is modulated at the transcriptional level is still unknown. The present study used arecoline, arecaidine and safrole, which are thought to be major toxic ingredients in BQ, as candidates to explore the role of TIMP-1 expression in OSF pathogenesis. Fresh tissue biopsies of oral mucosa from 20 OSF males were included in this study, and fibroblasts were cultured from one OSF buccal mucosa and one normal buccal mucosa of the same OSF patient. To quantify the TIMP-1 expression, enzyme-linked immunosorbent assay (ELISA) was used in the present study. The results indicated that OSF fibroblasts produced more TIMP-1 protein (569.2+/-79.5 ng/ml) than normal fibroblasts (303.0+/-59.3 ng/ml) from the same patients, and the mRNA expression of TIMP-1 in OSF fibroblasts was higher (1.76 fold) than normal fibroblasts of the same patients. Arecoline and safrole significantly elevated TIMP-1 protein and mRNA expression. We concluded that increased mRNA expression of TIMP-1 in buccal mucosal fibroblasts by arecoline and safrole is a possible pathogenesis for oral submucous fibrosis.