A Lymphomas case was treated with whole body irradiation. The results showed that micronucleated cell frequency and micronucleus frequency were very similar between the blood samples irradiated in vitro and in vivo. The differences were not singnificant (,p,>,0.5). The patterns of the curves obtained from regression analysis were identical, and the differences among the two regression equations of the same parameter were not singnificant, it is considered that dose effect was almost the same between the blood samples irradiated in vitro and in vivo in certain dose extent. The micronucleus frequency of human peripheral blood lymphocytes could be applied as a supplementary criterion fordose estimation to irradiated human at early stage of nuclear accident.