The Institute of Radiation Protection and Nuclear Safety (IRSN) organized a biological dosimetry international intercomparison with the purpose of comparing (i) dicentrics yield produced in human lymphocytes; (ii) the gamma and neutron dose estimate according to the corresponding laboratory calibration curve. The experimental reactor SILENE was used with different configurations: bare source 4 Gy, lead shield 1 and 2 Gy and a 60Co source 2 Gy. An increasing variation of dicentric yield per cell was observed between participants when there were more damages in the samples. Doses were derived from the observed dicentric rates according to the dose-effect relationship provided by each laboratory. Differences in dicentric rate values are more important than those in the corresponding dose values. The doses obtained by the participants were found to be in agreement with the given physical dose within 20%. The evaluation of the respective gamma and neutron dose was achieved only by four laboratories, with some small variations among them.