The review of literature related to tests of shear strength of municipal solid wastes is presented in the first part of the paper. It was revealed that MSW have very various values of angle of internal friction and cohesion, which are depended from composition of wastes, degree of biodegradation, test methods (type of tests, range of strain). It was stated, that the influence of aforementioned factors is often unclear, what causes that the choice of shear strength parameters of MSW for slope stability analysis is complicated. Slope stability analysis of examplary sanitary landfill in Chełmek is presented in the second part of paper. The shear strength parameters of wastes were taken from the first of paper. It was revealed that typical slope stability calculations gave high value of safety factor, whereas probability analysis show that expected performance level of sanitary landfill is between poor and below average.