This contribution describes the introductory part of an extensive research of the relationship between the size of municipalities and cities and their management and administration. Its task is to analyse the amount of entrepreneurship of municipalities and cities in the Czech Republic. Based on statistical data about companies owned by municipalities and cities, it shows that, despite the strong political conditionality of city administration, there are regularities in their business “behaviour”. The contribution describes both these regularities and their disturbances – in cities, business sectors and in specific companies. The size and complexity of urban subsystems – such as road networks, public spaces, the cultural sector, etc. – are closely related to the size of the city. Starting from a certain size of the city, challenging problems arise, which the ordinary office is not able to cope with. Therefore, the contribution also deals with finding these threshold values for the size of cities.