  We examine the evolution of the sizes and number densities of disk galaxies
using the high resolution images obtained by the Great Observatories Origins
Deep Survey (GOODS) with the Advanced Camera for Surveys (ACS) on the Hubble
Space Telescope (HST). The multiwavelength (B,V,i,z) images allow us to
classify galaxies based on their rest-frame B-band morphologies out to redshift
z = 1.25. In order to minimize the effect of selection biases, we confine our
analysis to galaxies which occupy the region of magnitude-size plane where the
survey is almost 90% complete at all redshifts. The observed size distribution
is consistent with a log-normal distribution as seen for the disk galaxies in
the local Universe and does not show any significant evolution over the
redshift range 0.25 < z < 1.25. We find that the number densities of disk
galaxies remains fairly constant over this redshift range, although a modest
evolution by a factor of four may be possible within the 2-sigma uncertainties.
