Symptoms of Attention Deficit/Hyperactivity Disorder (ADHD) have been documented in medical literature since the late 1700s, but were not serendipitously treated until 1937, when Benzedrine was observed to improve the behaviour and school performance of children with severe headaches. Craig Earl of INC Research examines how symptoms and treatments have developed, and describes how the remaining challenges continue to be the proper diagnosis and treatment of adults with ADHD.