Agarose gel electrophoresis is a powerful technique for the separation of nucleic acids on the basis of their size and conformation. The development of methods to recover size-fractionated nucleic acids molecules from agarose gels has greatly facilitated recombinant DNA technologies. Although several methods for recovering DNA and RNA molecules have been developed during the past fifteen years, none of them has been universally accepted. In this review we describe, discuss and evaluate the most common procedures with which we have had experience. Our evaluation is based on the criteria of yield, purity, speed, simplicity and low cost. We have considered three different approaches to the problem of recovering nucleic acids: chemical gel dissolution, physical gel disruption and physical extrusion from intact gels.