Summary Septoria leaf blotch caused by Mycosphaerella graminicola is one of the most important diseases of cereals. The pathogen belongs to species rapidly developing resistance to used fungicides. The increase of resistance of M. graminicola isolates to strobilurin in western Europe was already recorded in 2002, while in Poland about 10 years later. The aim of the study was to develop a PCR-RFLP (polymerase chain reaction – restriction fragment length polymorphism) assay for the identification of mutation (G143A) in cytochrome b gene of M. graminicola, which confers resistance to strobilurin. The analysis enabled to distinguish strains of M. graminicola resistant and sensitive to strobilurin, and it can be used for rapid monitoring of M. graminicola resistance to this group of fungicides.