The bachelor thesis deals with the issue of pesticides, including also their residues, specifically their negative impact on humans and environment. As their global use varies in relatively large numbers, the relevance of this topic is still relatively high today. The beggining of the work is devoted to a general overview of pesticides, which focused mainly on the toxic side and their individual properties. The fate of pesticides within the body of the organism and the environment is further discussed in the work. In addition, specific analytical methods that are key in residue monitoring are also discussed. The active substances of the selected pesticidal preparations which are currently in use are also described. In the final part of the work I try to demonstrate the bad but also good side of the use of pesticides throught specific situations that have taken place in the past and changed the perspective on pesticides, which are still among the most controversial topics.