AbstractThe upper limit of the size range of DNA amenable to separation in agarose solutions above their gelling temperature, using capillary zone electrophoresis apparatus, was increased to 12 kb. The plot of log(bp)vs.mobility derived from electrophoresis in 1.7% agarose solution is biphasic, exhibiting higher resolving power for DNA less than 1 kb in size than that of larger sizes. Resolving power for DNA larger than 1 kb increased when the agarose concentration was increased in the range of 1.0–2.6%. It was similar in solutions at 40°C of SeaPrep and SeaPlaque agaroses as well as in Acrylaide (trade names are those of the manufacturer). However, the resolving power of SeaPrep agarose at 25°C was inferior to that at 40°C. Concave plots of log(mobility)vs.concentration of the agarose solutions are those predicted under the assumption that the effective “equivalent radius” of the DNA molecule diminishes with increasing agarose concentration in the investigated concentration range up