Aggressive behavior is a very complex phenomenon and is commonly a part of child development, which occurs in various forms. Every day more and more children show unacceptable behavior, especially aggressive. It is expressed in various situations, most often in families and educational institutions, ie kindergarten. Aggressive behavior is a socially unacceptable behavior that has the intent to harm people or property and is most prominent in preschool age. Of all forms of behavioral disorders, aggressive behavior is most often described and investigated, but it is extremely demanding to define it unambiguously. The term aggressive behavior represents a whole series of different actings and emotions, and most often it is followed by other problematic behaviors, especially outsourced. Aggression can be an expression of helplessness or have the purpose of brutal pursuit of an interest. The causes of aggressive behavior are very complex, and the most frequent factors include family circumstances, gender differences, temperament, cultural factors and wider social context. The role of adults, parents and educators, is to teach the child how to achieve a desired goal in a socially acceptable way, to have control over emotions and to respect the needs and emotions of others. In this way prevention is achieved that can prevent the appearance of aggressive behavior. It is very important to spot early on the potential forms of problematic behavior and to prevent its development in timely pedagogical intervention. Aim of this paper is to show the characteristics and types of aggression, to give rise to the causes of aggression and risk factors, scientific theory of occurrence and the appearance of aggressive behavior in terms of sex and age. There are also methods of preventing aggressive behavior as well as appropriate procedures in dealing with aggressive children. At the very end of the work there is a case of a four year old boy and we wanted to establish certain possible causes of behavior.