ABSTRACT
Attention deficit hyperactivity disorder ADHD is a behavioral disorder which mostly affects children in the age group of six to eleven years. The disorder affects boys more than girls. Although difficult to assess in infancy and toddlerhood, signs of ADHD may begin to appear as early as age of two or three, but the symptom picture changes as adolescence approaches. Many symptoms, particularly hyperactivity, diminish in early adulthood. However, impulsivity and inattention problems remain with upto 50% of ADHD individuals through their adult life. Recently there have been studies on correlation between ADHD and bacterial and viral infections in brain. This review focuses on possible role of various viruses and certain bacterias in development of ADHD in children.