Gels of methoxylated agarose (gelling point 25.6 °C) and other low-melting agarose derivatives compare favorably with cross-linked polyacrylamide gels for capillary and slab molecular-sieve electrophoresis of proteins and DNA. These agarose gels can be pressed out of the capillary following a run and replaced by an agarose solution with a temperature of 35–40 °C. Gelation occurs upon lowering the temperature and the same capillary can thus be reused for another analysis with a fresh gel. The methoxylated, non UV-absorbing agarose gels are, accordingly, replaceable, which makes them very attractive for series analyses with modern, automated capillary electrophoresis apparatus. The high resolution of these agarose gels is demonstrated with a separation of an albumin sample into monomers, dimers, trimers, tetramers, pentamers, hexamers, heptamers, and of DNA fragments.