There is often a question of using pesticides. Application of pesticides must be responsible and not harmful to humans, animals and the environment. Pesticides are created and used to destroy insects, fungi, weeds, viruses and bacteria. Due to their great use, it is common for the appearance of pesticide residues in food, which has a long-term effect on human health, and is often discovered later. Special groups of pesticides are insecticides used in the control of harmful insects that may be vectors, parasites or cause harmful reactions in the environment and on human health. This work wants to get acquainted with the properties, types and manner of application of pesticides, with particular emphasis on insecticides, and be familiar with the risks. This paper presents an example of the most common DDT insecticide activity. Work has also introduced the legislative system on pesticides in Croatia and the European Union.