  It is generally accepted that the observed CMBR dipole arises from the motion
of the local group relative to the CMBR frame. An alternative interpretation is
that the dipole results from an ultra-large scale ($\lambda > 100 c/H_0)$
isocurvature perturbation. Recently it was argued that this alternative
possibility is ruled out. We examine the growth of perturbations on scales
larger than the Hubble radius and in view of this analysis, we show that the
isocurvature interpretation is still a viable explanation. If the dipole is due
to peculiar motion then it should appear in observations of other background
sources provided that they are distant enough.
