Setaria sphacelata is a tropical forage grass, cultivated in diverse regionsdue to its plasticity. Like other summer perennial forages, it has a slow establishment. Hydration-dehydration (HD) pregerminative treatments improve the germination and establishment of many species. The objective of this work was to evaluate the effect of HD with water and potassium nitrate on Setariasphacelata seeds. A factorial treatment design of 2 x 3 x 2 was applied. The first factor was the imbibitory agent: water (A) and potassium nitrate at 2 % (N); the second the imbibition time: 24, 48 and 72 hours; and the third the lot evaluated (two). Four repetitions of 50 seeds per treatment and one control (T) were sown. Germinative energy, germination percentage, fresh and dead seeds (SM) were recorded. Between lots, only significant differences were found in SM. The treatments A24, A48, A72 and N24 were better than T in speed and percentage of germination, while N48 and N72 were similar or inferior. It is concluded that HD treatment with water for 72 hours proved to be the best treatment. Immersion for more than 24 hours in potassium nitrate at 2 % impaired seed viability.