In a study of marine stratiform clouds on Tenerife in the Canary Islands, droplet concentrations were highly correlated with clear-air equivalent cloud water concentrations of non-sea salt sulfate (NSS), nitrate, and pollution-derived trace elements. Lower correlations with sea salt sodium and crustal aluminum indicated that these sources did not contribute to high concentrations of cloud condensation nuclei. High correlations of NSS and droplet number concentrations with those of pollution-derived trace elements (non-crustal V, Sb, Se) suggest that emissions from oil and coal combustion and other industrial sources in Europe controlled cloud microphysical variations in the southeastern North Atlantic. ¿ 2000 American Geophysical Union