Phytoremediation using an arsenic hyperaccumulator, Pteris vittata L., has generated increasing interest worldwide, for it's both environmentally sound and cost effective. However, the mechanisms of arsenic uptake and accumulation by this plant are not clear at this time. This study shows the uptake of arsenate (As(V)) and arsenite (As(III)) using a hydroponie culture of P. vittata. The fern takes up both As(V) and As(III) from the culture which spiked with 50 mg of arsenic per litter, and can grow within 5 days of experimental period. Final amount of arsenic accumulated in the fern is 3.2 mg (As(V)), and 3.8 mg(As(III)). Although about 10% of the culture solution was decreased per day by transpiration of the fern, the arsenic concentration in the solution is not changed to the initial value in both cases. This result means that most of arsenic, both arsenate and arsenite, are transferred into the plant from root with a flow of water absorption.