The objective of the study was to determine changes in the antioxidant capacity and polyphenol content occurring during the processing of cultivated mushrooms by lactic fermentation carried out using a starter culture of lactic acid bacteria (LAB). The investigation material consisted of mushrooms: Agaricus bisporus and Pleurotus ostreatus. The mushrooms blanched with the addition of salt, sucrose and spices were fermented using L. plantarum. After first week, the fermented mushrooms were placed in a cool room at 4-6 deg C, there, they were stored for 7 weeks or they were pasteurized. The antioxidant capacity values of fermented mushrooms et the end of cold storage were 22.1 and 2.8 micro M of Trolox/g d.m. as or A. bisporus and P. ostreatus, respectively. The antioxidant capacity was strongly correlated with the total polyphenol content