The micronucleus test on mammalian bone marrow is widely accepted as a
''screening'' test for chromosome anomalies induced by clastogenic ag
ents. The frequency of micronucleated polychromatic erythrocytes (MNPC
Fs) in the bone marrow of mice treated with cyclophosphamide (CP), ble
omycin (BLEO) and benzidine (BZN) was determined in three different la
boratories. Although dic experiments were conducted independently, the
results were quite similar for all three laboratories. The mean MNPCE
frequencies induced by CP and BLEO were not statistically different.
Only for the group treated with a single BZN dose were the mean freque
ncies statistically different between laboratories two and three. The
homogeneous results obtained by the three laboratories for the micronu
cleus test indicate the efficacy of the method and its applicability f
or the identification of clastogenic agents.