Conclusion This review illustrates how molecular and structural analyses have contributed to a greater understanding of the rich biological diversity seen in the picornaviruses. In many cases the second phase of studies, based on increasingly powerful genetic engineering, biochemical and immunological techniques is now well under way and beginning to reveal the depth of the vast store of information which still lies encoded cryptically in the sequences and structures which have been determined. The advances made already suggest that the next few years will be even more fruitful than those since 1981 when the first picornavirus sequence was published.