Behavior Therapy is based on Applied Behavioral Analysis (ABA). ABA is a study about learning procedures and human’s behavior. ABA is systematic, evidence based approach aiming to teach important skills for successful social functioning. Therapists manage to replace undesirable behavior with socially adaptive behavior by manipulating its antecedents and consequences. Therapy starts with observing and estimating one’s behavior, analysing data bases, preparing individual working plans and monitoring to fulfill them in practice. The process is focused on developing critical skills (e.g. communication, adaptive behavior) and decreasing problematic behavior (e.g. aggressive or self-harming behavior).