Ignition delay times of mixtures of n-C4H10 and i-C4H10 (1.0% C4H10 and Phi = 0.72 diluted in Ar) have been measured behind reflected shock waves by monitoring time histories of UV emission and pressure in the temperature range 1200-1600 K. The ignition delay time of i-C4H10 was longer than that of n-C4H10. It is also found that the ignition delay time of i-C4H10 decreased with the addition of n-C4H10. A detailed chemical kinetic mechanism for the high temperature oxidation of mixtures of n-C4H10 and i-C4H10 has been constructed. Rate constants for important reactions used in the model were selected from reliable literature values and were not adjusted as parameters. The model can reproduce measured ignition delay times by less than 25% accuracy, and the temperature dependence of simulated ignition delay times is in good agreement with experimental data. The difference in combustion characteristics between butane isomers is discussed on the basis of the chemical kinetic mechanism.