Optimization of arsenic uptake by Pteris vittata may reduce the remediation time and cost of arsenic-contaminated groundwater. This greenhouse experiment evaluated the effects of five doses of P (0, 150, 300,450 and 60011,M P) and two fern ages (45 and 90 d old) on the effectiveness of arsenic removal using 18 L of contaminated groundwater per plant. Arsenic-depletion was monitored weekly over a period of 74 d. It took 38 d for 45-d ferns in the no P treatment to deplete the arsenic to the target concentration of 10 mu g L-1 from 126 mu g L-1. During the 74-d study, the best treatment for 90-d ferns was at 150 mu M of P, reducing the arsenic concentration to 12 mu g L-1. Because arsenic uptake and removal is inversely related to the P-status, P-free Hoagland solution would maximize arsenic uptake in a short term. However, on a long-term basis, ministering the 0.2-strength Hoagland solution at 150 mu M P may be an effective approach for maximizing plant biomass production and arsenic removal. Published by Elsevier B.V.