A bachelor thesis is devoted to expert activities in the field of environmental sciences. In the first part defines an expert and his legal position in the legislation of the Slovak Republic, an expert opinion and his assessment, laws, rights and duties and responsibility of the expert according to valid legislation. In the second part analyses a content delimitation of specialization and branches of expert investigation in the field of environmental studies and in the third part deals with selected expert institutions and experts. The final part is the author´s personal contribution to this work. The importance of this work is to summarize information about expert activities in the field of environmental sciences.