Abstract This paper describes some nuclear changes during meiotic prophase of chick oogenesis at the light, and electron microscopic levels. The timing of each stage, and the morphology of the chromosomes and nucleoli at each stage, as described. Lampbrush chromosomes are found during diplotene, from ten weeks post-hatching to maturity. About five days after hatching large, mainly single, nucleoli appear in the chick oocytes. 3H-thymidine labelling, followed by autoradiography, is used to show DNA synthesis in the nucleolus, but not in the rest of the oocyte nucleus at this time. This suggests that the process of amplification of the ribosomal genes may take place during chick oogenesis.