The discovery of anaemia raises the question of its aetiology. If many causes can easily be established, some remain without any accurate diagnosis. The mere issue is that their causes can be rare or mechanisms interlinked. A blood film examination by the biologist provides helpful elements to guide the diagnosis, it can be improved if it is orientated by the physician who prescribed it. Two cases of late discovery of haemolytic anaemia, in relation with red cell membrane disorders, are reported. They illustrate the interest of a good collaboration between the physician and the biologist that lead to diagnosis. The first case is about a band-3 protein defect, the second deals with an hereditary dehydrated stomatocytosis.