In the last few years there have been considerable advances in the understanding of the molecular control of globin genes during development. Several insights have been obtained with studies using transgenic mice. The 5' to 3' order of the genes in the beta locus, the proximity of the genes to the locus control region and the availability of transcriptional factors have been implicated in the developmental activation of globin genes. Globin genes are turned off by two general mechanisms, autonomous gene silencing involving sequences located in the proximal and distal promoters and competition between genes for interaction with the locus control region. The current understanding of the control of embryonic (epsilon) and fetal (gamma) globin genes is reviewed.