The study was conducted under greenhouse (Temp. between 27 - 32 ºC and relative humidity 65%) and laboratory conditions of the Industrial Complex of the Equaquimic Company, located in the city of Quevedo province Los Ríos, at km. 4.5 via Quevedo – Valencia, coordinates 0°58'57.1" S and 79°26'28.9"W. to evaluate the mortality percentages of 20 ppm ozone dose under different exposure times (30, 45 and 60 minutes) on three of the most dangerous stored grain insect pests: Sitophilus zeamais (Motschulsky), Rhyzopertha dominica (Fabricius) and Tribolium castaneum (Herbst); separately for each insect with corn grains and without grains by direct exposure to each pest.Three experiments were performed, one for each insect species in a Complete Randomized Design (RCBD) in factorial arrangement (Time and condition). The results indicated that there were no significant differences in the interaction for insect mortality. The mortality was significantly affected by exposure time when corn was used or not. The mortality of ozone under 60 minutes of the exposure was recorded (< 90%), while 30 minutes, the shortest exposure time, showed average mortality of 81%; respectively for each insect species. In general, the average mortality in all exposure periods, with corn was 81%, while without corn was 98%for each insect species. These results demonstrate the efficacy of ozone as an alternative viable tool to control - stored grain insects.