Submicron aerosol number size distributions were measured on board the research ship Akademic Fedorov during a cruise from the English Channel to the coast of Antarctica. The observed sized spectra were fitted with three lognormal modes (the nucleation, Aitken and accumulation modes), and the data were classified according to calculated air mass back trajectories. The total particle number concentrations were mostly <1000 cm-3 in marine air masses and between about 1000 and 10000 cm-3 in continentally influenced air masses. Most of the eastern midlatitude Atlantic was affected by European pollution with high concentrations of both nucleation and Aitken mode particles. Another pollution peak, caused probably by biomass burning in Africa, was seen at about 10 N. Marine air masses showed distinctive latitudinal changes. Over the tropical Atlantic no nucleation mode could be seen, and the total particle number concentration remained usually below 500 cm-3. In the midlatitude and high-latitude Atlantic several episodes of elevated particle concentrations (<1000 cm-3) caused by either the nucleation or Aitken mode were observed. The geometric mean diameter of the accumulation mode decreased gradually toward the higher southern latitudes with a more rapid decline close to Antarctica. Our observations indicate further that there is no simple and universal relationship between the total particle number concentration, the submicron aerosol volume (or mass), and the number of particles able to act as cloud condensation nuclei over the southern hemispheric oceans.