The present status of various deuterium-tritium (D-T) neutron sources is given, including the prospects for improvements. By upgrading a Rotating Target Neutron Source II-type neutron generator, a yield of 1014 n/s can be achieved in a small volume. A yield of 1015 n/s is expected with construction of a gas-jet target. According to a proposal from Kernforschungszentrum Karlsruhe, a similar yield could be reached even with a volume of 500 cm3. Realistic fusion reactor conditions can only be satisfied by high-intensity D-T neutron sources. Other more economical or higher intensity accelerator-based neutron sources cannot replace them in this research field. The lack of sufficient financial support delays technically realistic projects. This difficulty might be overcome by a more intense joint international collaboration.