We put forward a novel 2-D graphical representation of DNA or RNA sequences based on a four-color map. The novel representation is rather compact and it not only enables one to carry out a visual inspection of similarity/dissimilarity between DNA sequences, but also leads to their numerical characterization. The approach is illustrated with the coding sequence of the exon 1 of the human P-globin gene. © 2005 Elsevier B.V. All rights reserved.