The uptake of cyanide by water hyacinths, Eichhornia crassipes (Mart) Solms in nutrient solutions enriched with 50, 100, 200 and 300 ppm cyanide was investigated. In pond water at 300 ppm cyanide, the water hyacinths could effectively absorb 6. 7 mg cyanide per gram dry weight of plant material. One hectre of water hyacinths has the potential of absorbing 56.8 kg of cyanide in a 72-hour period.