We investigate the effects of third-order dispersion on pulse width by using a femtosecond Ti:Al2O3 laser with independently adjustable second- and third-order intracavity dispersion compensation. A novel technique for compensating third-order dispersion is demonstrated using Gires-Tournois interferometers that are fabricated monolithically by using multilayer dielectric films. With the addition of intracavity third-order compensation, pulse-width reduction from 45 to 28 fs is achieved. The dispersion compensation effect produced by the Gires-Tournois interferometers is measured in situ using frequency-domain dispersion measurement techniques.