In this work, we present a new tool called Illustrator for Biological Sequences (IBS) for assisting experimentalists in drawing publication-quality diagrams of both protein and nucleotide sequences. With a dual-mode user interface, experimentalists are allowed to produce their own schematic diagrams for either protein or nucleotide sequences in a convenient manner. To provide a user-friendly software package, abundant graphical elements, such as polygons, brackets, curves and polylines, are available for representing functional elements or regulatory molecules. We anticipate this powerful tool will prove to be a great help to scientists for the purpose of visualizing biological sequences.