The effects of aqueous extracts of raw, baked and boiled areca nuts were tested on cultured human buccal mucosa fibroblasts. Cells were exposed to extract concentrations of 0, 50, 100, 150, 300 and 500 micrograms/ml. The arecoline and arecaidine content was determined in the extracts with HPLC and raw nut contained 5.5% m/m, baked nut 6.6% m/m and boiled nut 7.1% m/m. Extract concentrations of 50 to 150 micrograms/ml inhibited cell growth in a concentration-dependent manner but did not lead to total cell death during a 7 day period. However, total cell death did occur with concentrations of 300 and 500 micrograms/ml. It is concluded that areca nut extract is toxic to cultured fibroblasts and inhibits their proliferation in a concentration-dependent manner.