Abstract: The distribution of SCE among quail embryo cells coincided with Poisson distribution,while among chromosomes,it was nonrandom.There was a positive correlation (P<0.05) between SCE frequency and the chromosomal relative length,but SCE distribution in each chromosome was not completely in accordance with the relative length of each chromosome.The SCE frequency in each centromeric region was very high and accordance with the relative length of each chromosome.The per cell SCE average value was not significantly influenced by the sex of embryo (P>0.05),but that whether the SCE per Z was effected significantly by sex had not been determined.