DNA sequencing methodology was developed in the late 1970s (1 ,2 ) and has become one of the most widely used techniques in molecular biology. The amount of DNA sequencing performed worldwide has increased exponentially each year and this trend will almost certainly continue for the next few years at least. The importance of this technique is underlined by the volume of research funds now being channelled into genome sequencing projects, and by the large sums of money being invested in the development of automated sequencers and sequence analysis systems.