The advantages of purification by denaturing polyacrylamide gel electrophoresis (PAGE) are speed, simplicity, and high resolution. Although yields tend to be low (<50% of applied sample), the amount of material recovered is usually far in excess of that required for most molecular biology applications (e.g., cloning and sequencing). Denaturing PAGE can resolve oligonucleotides from 2 to 300 bases, depending on the percentage of polyacrylamide used. The method presented here is thus useful not only for isolating chemically synthesized deoxyribonucleotides but also small RNAs or other single-stranded polynucleotides.