Autism is a heterogenous spectrum od neurodevelopmental disorders defined on three basic bihevioral symptoms: impaired social interaction, comunication and a tendency for repetitive actions. There is a number of heterogenous disorders related to autism, which can be treated if diagnosed in early stages of life. Twin studies are the most common - they have proven strong genetic influence on developing autism symptoms, especially in monozygotic twins. Some autistic traits have been proven in close relatives of autistic children. Great number of genes related to autism lead to a conclusion that it is a polygenic disease which does not follow Mendelian rules of inheritance. Therefore, the key is in the interactions of certain genes that carry mutations. Epigenetic markers define the condition of chromatin and regulate the expression of genes without affecting the primary sequence of DNA. DNA methylations due to specific genetic mutations or environmental influence have been proven. These studies draw attention towards the importance of environmental triggers of autism, some of which have been recognized in several prenatal drugs. Disregulation of gene expression coding for the oxytocin receptor could be the possible cause of impaired affection noticed in many chilren with autism. Taken together, the cause of autism might be the interaction of different genes with the environmental factors. Future studies should focus on a more detailed classification of autism disorders, wherein timely diagnosis is of great importance.