Foliar leaching might be an important process in the biogeochemical cycle of elements, but the leaching behaviors of As remain unclear. This study examined As leaching from foliage of an As-hyperaccumulator, Pteris vittata L. in the field. Results indicated that substantial amounts of As can be leached from the foliage by precipitation. Arsenic concentrations in the foliar leachate ranged from 4.06 to 519 microgL(-1), and the percentages of As(III) with respect to total As in leachate ranged from 5% to 10%. A positive linear relationship existed between As concentrations of the foliar leachate and the amounts of As accumulated in the plant. The rate of As leaching from the leaves was accelerated by an increase of rainfall and time in a simulated precipitation experiment. Water-soluble As distributed within the cuticle and apoplast of the plant was speculated as the main source of the leached As. The As leaching is an important process of within-ecosystem As cycling in phytoremediation and it deserves further investigation.