The objective of this research was to study the efficiency of different treatments for breaking dormancy in rice seeds. To achieve the objective, the cultivar Cica 9 was used. Harvest of different fields and different environmental conditions of seed maturation, composed three lots. The treatments for dormancy breakage were the following: soaking for 24hours in 1% Sodium Hypochlorite (NaClO3); imbibition of the germination test substratum with 0,2% Potassium Nitrate solution; soaking for 24hours in water at 40ºC; soaking for 48hours in water at 40ºC; and dehulled seeds. The evaluations was done through standart germination test evaluated in five monthly dates. In parallel, the tetrazolium test was made to evaluate the viability of dormant seeds. The results showed that, in the conditions of the experiment, the different levels of dormancy in rice seed lots affected directly the treatments efficacy. Soaking for 24hours in 1% Sodium Hypochlorite was the most effective treatment. The tetrazolium test proved to be an efficient and fast method to estimate the viability rice seeds lots with different levels of dormancy.