Silica accumulation in plants was found to be influenced by environmental factors and growth conditions. But, the processes and patterns were reported to be extremely complex. To examine whether inter-specifica variations in silica concentration and other traits and relationships exist in responsse to moisture stress, we created different moisture levels in 3 tropical fodder grass species (Pennisetum purpureum, Panicum maximum cv. Cl and P. maximum Jacq.) by watering pots every 3 days (moisture-stressed) or every day (control), from January 4 to March 15, 2002. Leaf biomass of all species was decreased in response to moisture stress and leaves were yellow and wilted. A lower leaf biomass under moisture stress was associated with blades of higher specific leaf area and water content and lower silica concentration in P. purpureum but not in the Panicum accessions. Silica concentration ranged from 2.03% to 5.2% in blades and from 1.95% to 3.4 % in sheaths. P. maximum Cl had the lowest values, while P. purpureum showed the highest values. Increased silica deposition in well watered plants may result from higher transpiration reates. Silica was highly correlated with soluble ash in both species.