The aim of this study was to determinate microscopic fungi that can cause occurrence of mould in bread. We used breads from experimental baking with different addition of walnuts (0 - 15%) as model samples. Bread samples were stored in the fridge, in plastic bags and in the bread box. After three days of storage 25% of samples were moldy. The middle parts of breads (4 pieces), that were not moldy, were stored on DRBC and cultured at 25±1oC for three days. All the colonies of micromycets were inserted on identification agar. Molding of bread samples was caused by species of genera: Aspergillus, Penicillium, Cladosporium and Rhizopus. 28 strains of potentially toxigenic species of genera Aspergillus and Penicillium were tested by TLC method for the ability to produce chosen mycotoxins in conditions in vitro. We discovered the production of cyclopiazonic acid, penitrem A and roquefortin C using mentioned method.