Reticulocytes are the last stage of erythropoiesis before red blood cells (RBC). Although most of the RBC proteins have been characterized, little is known about expression profile of their mRNA during differentiation. Our goal was to initiate a genomic global solution to provide a transcriptional data base on which it will be possible to follow the erythroid differentiation and study RBC disorders. We used a modified protocol of serial analysis of gene expression (SAGE), the serial analysis of downsized extracts (SADE) which allows identification of genes from small amounts of mRNA and is thus an appropriate method starting from reticulocyte. SAGE does not depend on previous knowledge of genes. The method produces a set of cellular transcribed gene signatures (tags) and provides a comprehensive view of cells phenotypes by computational analyses.