Tomato seeds of the cultivar IPA-5 were submited to an atmosphere of 42°C temperature and 95-100% relative humidity for periods of 24, 48, 72 and 96 hours, regarding to determine the best aging period to evaluate seed vigor through the accelerated aging method. Periods of 24 and 48 hours were considered ?not sufficient? and the ?96 hour - period? was considered too much detrimental to the seed the ?72 hour-period? was supposed to be the most suitable. No correlation was observed between the results of the accelerated aging test with the results of field emergence test.