Most results of the Institute is achieved in the international collaboration. The scientists of the Nuclear Physics Institute are intensively collaborating with colleagues from several tens of institutions in Europe, America, Asia and Africa.
Important are participations in large international experiments unfeasible within a small country. Let us mention the collaboration TAPS in relativistic heavy ion collisions where properties of nuclear matter under extreme conditions are studied in experiments performed at GSI Darmstadt. The collaboration HADES (High Acceptance Dilepton Spectrometer) builds at GSI a new detector to study the masses and lifetimes of the rho and omega mesons produced in heavy ion collisions .
Other international experiment NPI takes part in runs at GANIL Caen, where exotic light nuclei with high number of neutrons are studied. The results of participation at TAPS and GANIL are described here and here in detail.
Nuclear Physics Institute benefits from the membership of the Czech Republic in CERN and in JINR Dubna . In CERN, we participate in the projects WA98, ALICE and ISOLDE.
Quark-gluon plasma formation in heavy ion reaction will be searched for at the experiment WA98 and by the ALICE collaboration where NPI participates in preparation of an experiment at the future Large Hadron Collider (LHC) .
A common proposal with the Oxford University concerning the beta decay of nuclei oriented at low temperatures is submitted for ISOLDE committee.
Participation at JINR Dubna concerns mainly nuclear spectroscopy on the beam, neutron physics, nuclear reactions with exotic nuclei and heavy ions, and dosimetry.
Foreign experimentalists are also measuring at the Nuclear Physics Institute, especially using the highly sensitive neutron difractometers but also our other facilities.
The international collaboration of theoretical physicists of NPI, besides many purely theoretical results, led to the performed experiments and/or to the experimental proposals on the world-leading research centers as KEK Tokyo, PSI Villigen, INFN Rome, MAMI Mainz, and CEBAF Newport News (Virginia) in the area of intermediate energy physics.
Nuclear Physics Institute is regularly organizing a few series of international scientific meetings. The one with the longest tradition was the 5th Symposium Mesons and Light Nuclei . The Conference on Rigorous Results in Quantum Dynamics  was organized and the Conference on Mathematical Results in Quantum Mechanics  has been co-organized. The Summer Schools on Intermediate Energy Physics [5, 6] and the Schools on Relativistic Heavy Ion Physics, intended for students and young physicists, are held every year and developed from a modest internal activity into respected international event. IAEA Training Course ``Dosimetry in Radiotherapy'' has been also organized.