A model bone marrow chromosome aberration test using the chick, Gallus domesticus, is described. The well known reference mutagen mitomycin C was used as the test chemical. Bone marrow chromosomal preparations were investigated after acute (0.5, 1.0, 2.0, 3.5 and 5.0 mg/kg b.w.) doses for dose-response and sub-acute (0.4 mg/kg/day, 5 days) doses for chronic studies. Only a single dose (2 mg/kg b.w.) was employed for time-response (6, 24 and 48 h) and route-response (i.p. and p.o.) studies. All the treated results differed significantly from the respective control value. The present results also revealed the location of a 'hot spot' in chromosome 4. The test is less expensive, more sensitive and reliable and easier than mouse model. This chick mutagenicity test model can be used as an alternative in vivo system for testing the mutagenicity of environmental pollutants.