Biological dosimetry, based on the analysis of dicentric chromosomes, is an internationally established, independent method applied in the area of radiation protection. The biodosimetry is mainly performed, in addition to physical dosimetry, with the aim of individual dose assessment, especially after unclear or suspected radiation dose exposures. However, a new biodosimetrical challenge has emerged in recent years in the form of a possible large scale radiation accident potentially involving large numbers of exposed persons. In order to be prepared to act in an efficient manner in such an accident, the established cytogenetic laboratories have increased their cooperation at the national and international level. General experience and results of intercomparisons are reported and future options to increase sample throughput are outlined.