In general, tropical pastures have limitations of use under conditions of stress by flooding. The purpose was to measure the flooding stress response in dry biomass and root/shoot ratio of five accessions of Paspalum (Paspalum regnellii, BRA 23469, BRA 23540, BRA 23671 and 21377 BRA) and Brachiaria brizantha cv. Marandu at the end of the stress period and after recovery under ideal water conditions. The greater shoot biomass was observed in Brachiaria brizantha, being similar among Paspalum accessions. The root biomass and the root/shoot were negatively affected by flooding and also by the collection period at the end of 28 days of stress. Flooding considerably influenced biomass allocation to roots and root/shoot ratio Paspalum genotypes. The allocation model is important for understanding the strategies adopted by these plants to acquire competitive advantages under water stress