Introduction: Plastics as an ubiquitous material are exposed to weathering in the environment, where they break down into smaller particles (< 5 mm) called microplastics. Agricultural activity (usage of plastic foils, usage of compost and waste sludge as fertilizer) is the main source of microplastics in the terrestrial environment. Microplastics is a pollutant that poses a great risk to human health. Well-developed analytical methods are crucial for assessment of the microplastic contamination in the terrestrial environment. Purpose: The purpose of the master's thesis was development of a method for extraction, quantification and identification of microplastics from soil. We wanted to develop a method for different density plastic polymers and for soil samples with different levels of organic matter. We focused on the five most common polymers polyethylene, polypropylene, polystyrene, polyvinyl chloride and polyethylene terephthalate, which occur in soil and compost and consequently on agricultural land. Methods: The development of the extraction method was done by comparing the oil extraction and the density separation method. The methods were optimized for compost samples. In the method of identification of microplastics by gas chromatography–mass spectrometry, we optimized the process of melting microplastics. At the end we tested the method on the five most common polymers and soil and compost samples. Results: The average efficiency of oil extraction was 97.8 % and for density separation method 97.5 %. To extract microplastics from the compost samples, an oxidation step before and after extraction was added. The average efficiency of the developed extraction method was 97.8 % ± 3.3 %. To identify the polyethylene terephthalate, it had to be separated from the remaining polymers during the melting process. All five most common polymers were confirmed with the identification method. Discussion and conclusion: The efficiencies of these methods are comparable, but density separation method is faster and easier to perform for the compost samples. A new characteristic compound for the identification of polyethylene terephthalate has been evident in the identification method. The identification method also showed the possibility of quantification of microplastics. Further optimization of these methods will enable the assessment of microplastics pollution in the environment.