Psychiatric disorders are difficult to explain from an evolutionary aspect, since it is hard to reason how a characteristic carrying a reproductive disadvantage survives through natural selection. There are several evolution-based papers concerning obsessive-compulsive disorder (OCD), which aim at resolving this contradiction. Recent studies provided considerable evidence in support for the evolutionary theories of OCD. Research confirmed an important role for genetic factors in the background of OCD, and neuroanatomic studies supported that neuroanatomical structures playing a role in OCD are those areas which are activated during the processing of danger and threat. From the evolutionary aspect OCD can be explained both from the individual and group selection aspect. According to the theory of individual selection, OCD symptoms are based on such behaviors which are by themselves advantageous serving individual survival and reproduction and therefore carry on through natural selection. According to group selection theory, although OCD is disadvantageous for the individual, it is adaptive for the survival of the group. In our paper we review the individual and group selection theories of OCD, and we also outline the continuity and discontinuity theories which show a significant overlap with the evolutionary theories. We review characteristic age and gender differences related to OCD from this aspect. The evolutionary approach to OCD is important in understanding the background factors, development and symptoms of OCD, which mean new tools in the prevention and treatment of this disorder.