This objective of this research was to evaluate the changes that occured during the dormancy in irrigated rice seeds, stored under different conditions of temperature and water content, evaluated for germination, the α-amylase enzyme activity was also used as an indicator of the intensity of seed dormancy. Seeds of the Urucuia cultivar possessing high intensity of pos-harvest dormancy were used. Seeds were packed in multilayer paper bags and stored during a 12 month period, in conventional warehouse and cold chamber environments, in Lavras and Patos de Minas/ MG/Brazil. Every three month the α-amylase activity was determinated by using the polyacrilamide gel electrophoresis and spectrophotometry. At the same time, the germination test was performed. Results indicated that in a cold chamber environment the dormancy break of seeds was slower than in conventional warehouse environment. The changes in the α-amylase activity profiles suggestted that this enzyme is a promissing indicator of the rice seeds dormancy level.