An immunocytochemical method using a specific monoclonal antibody was employed to detect DNA polymerase α in Drosophila melanogaster embryos during the first 13 nuclear division cycles after fertilization. The anti-DNA polymerase a antibody stained the ooplasm of the unfertilized egg, indicating that DNA polymerase a is maternally stored. Strong nuclear staining with the antibody over the weaker staining of the cyto-plasm was observed at interphase throughout the 13 nuclear division cycles. The staining of the cytoplasmic regions surrounding the nucleus was much stronger than the other region of the syncytial cytoplasm until cycle 10. Although prophase nuclei were stained with the antibody, metaphase chromosomes were never stained through-out the 13 cycles. The chromosomal (nuclear) staining reappeared at anaphase until cycle 11 and at telophase in later cycles. The staining of the syncytial cytoplasm except for the cortical region became faint by cycle 13, suggesting the consumption of the maternal storage by this cycle. These results suggest that DNA polymerase a dissociates from chromosomes at the beginning of metaphase; then in later mitotic phases, it is transported from the syncytial cytoplasm into nuclei to participate in formation of the active DNA replication enzyme complex.