The effect of ozone against immature stages of the potato tuber moth (PTM) Phthorimaea operculella was investigated. The immatures (Eggs, the newly hatched larvae, 12days old larvae, and pupae) were exposed to ozone concentrations using two procedures. Thirty of isolated stages (first procedure of exposure) and 5 of infested potato tubers contain a separate stage of PTM (the second one)  were exposed toozone concentrations 50, 100, 200, 400, 600, 800 and 1000 ppm in a combination of different exposure times 2, 4, 6 and 8 hours. All results indicated that mortality percent of all insect stages increased by increasing the concentration and exposure time. The effect of ozone concentrations was higher on the isolated numbers of immature stages in the first procedure of exposure than that within potato tubers in the second one. The newly hatched larvae in both procedures were the most sensitive stage to ozone, it completely killed when exposed for 8hrs at 50 and 200 ppm in the first procedure and second procedure, respectively. While the elder larval stage was the least sensitive one. At the highest concentration and the longest exposure time (8hrs), larval mortality was 82.2 and 68.5 % in the two procedures, respectively. Also, sprouting  of potato seeds was enhanced when treated with ozone concentrations compared with untreated seeds.