The accession of the Republic of Croatia to the European Union and its adaptation to the acquis communautaire and the common market has brought many changes to the economic entities operating in the energy market. Liberalisation as one of the basic requirements of the European Union in the segment of gas supply implies new rules and the emergence of competition in, until then, a monopolistic gas market, bringing about significant changes in the business of companies owned by public authorities, especially those operating in the energy market. These changes can lead to opportunities or problems, with the latter potentially escalating into a crisis. Early warning signs of an upcoming crisis are the basic elements of a timely response. Enterprises owned by the state and the local government are in a specific position, considering that the primary objective and the reason for such organisations to exist is to meet the public needs, while successful business and a finacial gain are of secondary importance. The internal gas market became a part of the European market regulated in accordance with the European acquis, the basis of which is the free movement of goods, capital and workers. The emergence of competition whose main objective is earning profit is the normal development of events to which public companies owned by the public authorities have to adjust and find the balance between meeting the public needs and achieving positive business outcomes. Significant changes in the external business environmet require an alignement and adaptation to new circumstances, and the failure to adjust leads to a failure in results, or a business crisis. In this graduate thesis I analyse the business in the new conditions of the liberalised gas market, and identify the danger of a business crisis using the example of a company owned by the public authority of the Zagreb Gas Supply Company "Zagreb-Opskrba Ltd.", the leading supplier of natural gas to customers connected to gas distribution systems in the Republic of Croatia.