Post-translational modifications of histones modulate the functional landscape of chromatin and impinge on many DNA-mediated processes. Phosphorylation of histone H3 plays a role in the regulation of gene expression and in chromosome condensation/segregation. Certain evolutionarily conserved residues on histone H3, namely Thr3, Ser10, Thr11 and Ser28, are phosphorylated during interphase or mitosis in both metazoa and plants. However, many of the kinases involved in these events appear to have evolved independently in different lineages. Likewise, the mechanistic function of specific phosphorylated amino acids, although poorly understood, also seems to differ among eukaryotes. Moreover, some modifications, such as phosphorylation of histone H3 Ser10, appear to have both a positive and a negative connotation and only become meaningful in combination with other histone marks within a particular chromatin context. Thus, a detailed understanding of the influence of histone H3 phosphorylation on biological processes may require learning organismal dialects of the histone code. © 2009 Landes Bioscience.