  We explore how the growth rate of spiral disks can be measured via analyses
of the scatter in the Tully-Fisher (TF) relation of local and intermediate
redshift galaxies. As an initial step, we show it is possible to construct a
low-dispersion TF relation for nearly face-on, nearby spirals. We find these
spiral disks are non-circular, (a mean ellipticity of 6%), which accounts for
about 0.1 mag of the intrinsic scatter in the nearby TF relation of even the
most ``normal'' looking spirals. If this ellipticity is induced by matter
accretion, we expect to find greater disk ellipticity or disturbance in the
past. We find evidence that more extreme outliers of the intermediate-redshift
TF relation are more morphologically and kinematically disturbed. Whether this
effect reflects a redshift trend or selection bias of local samples needs to be
addressed.
