This thesis presents the study on the use and knowledge of the speech variety used in Donja Stubica among pupils in elementary school (fourth graders) and elderly citizens. The thesis consists of four parts. The first part contains a brief portrayal of the city of Donja Stubica in which the geographical position of the city itself is presented, as well as the history and traditions characteristic of Donja Stubica that is regarded to be the centre of the southern part of the region called Hrvatsko Zagorje. The second part of the thesis is dedicated to the dialects of the Croatian language with a specific focus on the Kajkavian dialect where not only the contemporary situation regarding dialects of the Republic of Croatia is illustrated, but also the reasons for the decrease in the number of speakers of original idioms. Moreover, the categorisation of the Kajkavian dialect and the way it is spread is described as well. What is also mentioned are the most important events and individuals who contributed to the research and development of the dialect in question. The third part of the thesis refers to the characteristics of the speech variety spoken in the territory of Donja Stubica, i.e. it involves the analysis of its phonological, morphological, syntactical and lexical qualities. The last part illustrates the research in which primary school pupils (fourth graders) and elderly citizens participated. By using a written testing method, the aim was to gain an insight into differences in the way fourth graders and elderly citizens use the speech variety of the territory of Donja Stubica, in other words to what degree the aforementioned speech variety is used among pupils in primary school and the elderly who live in Donja Stubica. The research showed that primary pupils use considerably fewer lexemes that are characteristic of speech variety spoken in Donja Stubica compared to older participants. Another finding is the fact that fourth graders use more Standard Croatian, while dialect elements of the previously mentioned speech variety are gradually disappearing.