The feasibility of producing selenium-enriched water lettuce (Pistia stratiotes L.) was studied by cultivating water lettuce in Hoagland's solution containing 0, 20, 40, 60 an 80 mg Se from sodium selenite/L. There were 4 replicates in each Se concentration. Each replicate consisted of 30 plants of water lettuce. Three plants of water lettuce in each replicate were sampled on day 0, 1, 2, 3 and 4 of the experiment. The samples were washed with deionized water, separated for leaves and roots and finally dried at 65°C. Prior to Se determination, leaf or root samples were pooled by replicate. The finding revealed that Se concentrations in leaves and roots of water lettuce increased significantly (p<0.05) with increasing Se concetration in Hoagland's solution and day of cultivation. However, Se concentration in leaves was lower than that of roots. Water lettuce cultivated in the solution containing 60 fo 80 mg Se L^-1 exhibited the yellow leaves an died in day 2 and 3. Therefore, the appropriate Se concentration and duration for producing Se-enriched water lettuce were 20 to 40 mg Se L^-1 and 2 to 3 days of cultivation. The leaves of water lettuce cultivated in those conditions contained 11.14-13.50 and 21.06-29.55 mg Se kg^-1. respectively.