This study has been carried out using the onion and pepper seeds to determine the effects of the aqueous medium temperature, during treatment with oxygen, on the germination percentage seed vigor and for determining the period needed for the treatment with the oxygen as well. The treatment period has taken ١٢-٣٦ hours according to the kind of crop and the medium temperature, which varied between ١٠-٣٠ °C. Results of the study indicated that the treatment of seeds with oxygen, in an aqueous medium, improved the germination percentage and the seed vigor. The period needed for the treatment of the seeds with oxygen differs according to the kind of crop and the temperature of the medium and varies between ١٨-٢٤ hours with respect to the onion seeds, and between ٢٤-٣٦ hours regarding the pepper seeds. The period needed for treatment with oxygen decreases with the rise of temperature.