Life Cycle Assessment, which is considered to be one of the most effective methods of environmental management, is a useful tool to evaluate the environmental aspects of waste management systems. The LCA procedure is a complex task and requires a precise definition of the scope of a research, acquisition of a variety of accurate data, as well as a skillful selection of a method for assessing environmental aspects. This article aims to analyze the life cycle of the municipal waste management system in TarnowTarnów in 2012, using the IWM-PL model, the application in the Polish language version, launched in 2011. The functional unit is the total amount of municipal waste in the waste management system, i.e. the amount of mixed solid and selectively collected municipal waste, collected in Tarnów in 2012, and transported to materials recovery facility or to disposal. The boundaries of the system include recovery and disposal processes carried out in these facilities, as well as transportation of waste there. The IWM-PL model calculates emissions to air and water for the functional unit, and then converts them into six impact categories: carcinogens, respiratory system - inorganic compounds, respiratory system - organic compounds, climate change, acidification/eutrophication, ecotoxicity. Impact categories are assigned to two damage categories: human health and ecosystem quality. The performed assessment of the life cycle of the municipal waste management system in Tarnów in 2012 revealed a negative impact on the environment. The final result, expressed in eco-points (Pt), is significantly higher in the category of human health than in ecosystem quality. Emissions of methane and carbon dioxide from landfilling process greatly contribute to the value of the obtained result. The waste management system should be altered and the landfill of mixed municipal solid waste (including bio-waste) should be abandoned in order to reduce the negative environmental impact of municipal waste management in Tarnów.