The key of mutual integration of health care institutions lies in their interoperability, gathering and common utilization of data by different applications. Seemingly, imperceptible and smooth applications’ integration enables an efficient mutual linkage of all departments within a single health care institution as well as horizontal and vertical linkage of more health care institutions, all with the aim of improvement of health and quality of patient’s life. Health care system quality improvement needs a continuous rationalization of resources funds, which leads towards optimization of business processes and availability of all necessary information in the shortest possible period. All necessary information and data on patients must be available independently on location or time of such a necessity.

The greatest obstacles for interoperability represent heterogeneous applications. Such heterogeneity can be presented by the fact that they were written in various program languages, that they are intended for utilization at different types of computers or the fact that they use various communication networks and data transfer methods. IT managers in hospitals must decide how to contribute to cross‐organizational integration and what strategy and means to choose for achieving interoperability. If a system is poor in its interoperability, any increasing functions or little changes could stop its working properly. Interoperability must be ensured at technical, semantic and process levels but also in a legislative level, where all recommendations for legal and lawful solutions are given, which remove the most frequent obstacles – human and bureaucratic factors.

The Oncology Institute of Vojvodina as a referent center for oncology and a center for medical informatics signed its own Integrated hospital and business information system. The information system at the IOV consists of the following modules:
1. hospital‐clinical IS
2. laboratory IS
3. pharmaceutical IS
4. radiological IS
5. invoicing (accounting) IS
6. business IS
7. managerial IS

All of these modules are mutually optimally integrated, and their interoperability at the level of communicational protocols (HL7, DICOM, internal interface), semantics (the same code‐records, rules) and legislative level (the same accounting calculations) enables the user to see all these complex modules as one system.

Thus, we created necessary preconditions for our integration into information society, which is a 21st century strategy at the state level.