Denaturing HPLC was used to determine mutations occurring during the adaptive evolution of Escherichia coli K-12. The strains were evolved over 700 generations on glycerol as the sole carbon source from a sub-optimal to an optimal growth rate. The mutations detected by direct sequencing of amplicons of the glycerol-phosphate regulon repressor (glpR) gene were a synonymous substitution Val20Val in two separately evolved strains. Non-synonymous substitutions, Val119Gly and Gly179Trp, were also observed in each of the two strains. This procedure can be scaled to determine genome-scale sequence variations that have occurred during adaptive evolution.