Autistic disorder is a global developmental disorder that usually appears within the first 30 months of life, i.e. before the age of three. It affects almost all mental processes and lasts throughout a person's life. The disorder was first described by Leo Kanner in 1943 but it is still not known what exactly causes it. Most scientists discuss multiple causes of autistic disorder. It was considered that autistic disorders are rare and that 4 or 5 out of every 10 000 children born are diagnosed with autism. Also, it was believed to be more prevalent in boys than girls. However, more recent research suggest significant increase in prevalence in autistic disorders that is 1 in 100. The most common symptoms of autism are lack of emotional response to people and things, verbal and non verbal communication challenges, especially speech and language disorders, but also restricted, repetitive behaviour. Educating parents, family members and teachers of children with autism spectrum disorders may improve the children' s life quality. The aim of this diploma thesis is to introduce some basic features and characteristics of autism.