  Context: Giant-cell convection is believed to be an important component of
solar dynamics. For example, it is expected to play a crucial role in
maintaining the Sun's differential rotation.
  Aims: We re-examine early reports of giant convective cells detected using
correlation analysis of Dopplergrams. We extend this analysis using 19 years of
space and ground-based observations of near-surface horizontal flows.
  Method: Flow maps are derived through local correlation tracking of granules
and helioseismic ring-diagram analysis. We compute temporal auto-correlation
functions of the east-west flows at fixed latitude.
  Results: Correlations in the east-west velocity can be clearly seen up to
five rotation periods. The signal consists of features with longitudinal
wavenumbers up to m=9 at low latitudes. Comparison with magnetic images
indicates that these flow features are associated with magnetic activity. The
signal is not seen above the noise level during solar minimum.
  Conclusions: Our results show that the long-term correlations in east-west
flows at low latitudes are dominantly due to inflows into active regions and
not to giant convective cells.
