The estimation of presence and counts of microorganisms in oat and wheat bran produced by four Polish companies was the aim of this investigation. Microbiological assessment of bran samples included: total count of mesophilic, aerobic bacteria and their spores, occurrence of enterococci, coliform group bacteria and pathogenic bacteria and also counts of yeasts and moulds. The composition of fungal flora occurring in bran samples was also estimated. It was stated that the microbiological quality of the bran was variable. A considerable number of samples was characterized by high level of total count of bacteria and/or moulds and high level of coliforms and consequently they fell short of the standard requirements. However, no pathogenic bacteria was detected in the estimated bran. The ineffective heat treatment of the bran or repeated microbial contamination could be a reason of too high total count of microorganisms in the bran.