  I discuss observations of magnitude residuals from the B-band Tully-Fisher
relationship, B-V color, chemical abundance gradients, and asymmetries in the H
I and stellar disks of nearby spiral galaxies within the context of a model in
which small satellites or H I clouds are accreted onto the outer disks of
spiral galaxies. Correlations between the various observables support the
hypothesis that accretion dilutes the gas phase abundances in the outer disk,
steepens the abundance gradient across the disk, increases the star formation
rate, and creates asymmetries in the outer disk. By estimating the duration of
steep abundance gradients, elevated rates of star formation, or outer disk
asymmetries, constraints can be placed on the rate of accretion events. The
data suggest that accretion events at the current time are common.
