This bachelor thesis shows the influence of heterogeneity of mixed municipal waste on obtaining different results by performing a leaching test. For the purposes of the leaching test, samples from the functional waste management centers Marišćina and Bikarac are used, where daily amounts of incoming waste are measured in tons. For example, for Marišćina, the daily capacity is 350 t per day, and for a representative sample a mass of only 90 g was taken, which can affect the accuracy and representativeness of the results. In order to examine the impact of waste heterogeneity on such a small representative sample, additional random sampling is carried out. All samples are subjected to the laboratory leaching test with the aim of obtaining values for the prescribed parameters. The obtained values of the representative sample are compared with the values of randomly selected ones. After the deviations from the representative sample have been defined, they are expressed in percentages. The results of the research were analyzed and mutually compared. The comparison shows large deviations of some parameters in relation to the representative sample which should contain all the properties and characteristics of the mass from which it was taken. The deviations can be attributed to the extreme heterogeneity of the waste and the small mass of the sample. The results show deviations that vary on average from +100% to -250%, except for certain parameters which have larger deviations with very high percentage values. According to the results of the research, it was concluded that the representative samples does not show the real situation.