The effects on low-level cloud microstructures of varying aerosol regimes in the Arctic are examined using ground-based measurements obtained near Barrow, Alaska. Episodic 'arctic haze' events produced high cloud droplet concentrations, and small cloud droplet effective radii. By contrast, the fresh nucleation of aerosols within the Arctic produced particles high in number concentration but generally too small to be efficient cloud condensation nuclei. Comparisons with similar analyses done at lower latitudes suggest that the 'indirect effect' of haze aerosol on low-cloud effective radii is particularly high in the Arctic.