Whether bovine haemal nodes are involved in turnover of red blood cells has been a subject of some controversy In this study, fluorescent and conventional optical microscopy of conventionally or immunohistochemically stained node sections, together with transmission electrón microscopy, showed the presence of erythrocyte precursors and megakaryocytes, and evidence of active involvement in the destruction and replacement of oíd or degenerate red cells and the platelets.