Because betel quid (BQ) chewing has been linked to a higher prevalence of periodontal diseases, the pathobiological effects of arecoline, a main alkaloid found in areca nut, were investigated in cultured human gingival fibroblasts. At concentrations higher than 0.4 mM, arecoline inhibits cell attachment, cell spreading and cell migration in a dose-dependent manner. These inhibitory effects were associated with intracellular depletion of glutathione (GSH). At concentrations of 0.4 mM and 1 mM. arecoline depleted about 26% and 45% of GSH after 2 h incubation. Exposure of cells to areeoline at concentrations lower than 0.4 mM for 2 h showed no significant decrease in either cell viability or intracellular GSH. However, incubation of cells for 24 h in 1 mM arecoline decreased the cell numbers to only 35% of those in the untreated control. Arecoline also decreased cell growth and collagen synthesis in a dose-dependent manner. Because of repeated and long-term exposure to arecoline. BQ chewers could be more susceptible to periodontal damage and less responsive to new attachment procedures.