the prato, cheese washed dough, is one of brazil's most popular cheeses. this cheese must be ripened the desirable characteristics of flavors and texture. the present work studied the influence of gamma radiation in the ripening period of prato cheese. the cheese was ripened at 10-12oc and at ± 80% rh for 60 days. at the 1st and at 15th day of ripening, sample were irradiated to 0 (control), 1, 2, 3 and 4kgy at a rate of 0.9696kgy/h. the cobalto-60 source used was a gammabeam 650 from atomic energy of canada. physical-chemical and microbiological characteristics were analyzed every each 15 days of ripening. the results showed that the total microbial count decreased as increased the dose of irradiation of the cheese. the ripening of the cheese was delayed by irradiation, probability due to the inactivation of the lactic bacteria by radiation.