Daily aerosol samples collected at Bermuda and Barbados as part of the Atmosphere/Ocean Chemistry Experiment (AEROCE) were analyzed to evaluate the sources for selenium (Se). Isentropic trajectories were used to further evaluate the sources suggested by the chemical information. At Bermuda, the major source for Se was anthropogenic emissions from North America. Daily Se concentrations were highly correlated with antimony (Sb) which originated from a pollution source. However, approximately 6% of the Sb was associated with mineral dust from northern Africa that reached Bermuda during the summer months. The Bermuda aerosol data showed a weak correlation between Se and methane sulfonate (MSA), but the intercept of the Se versus Sb regression indicated that a marine biogenic source of Se accounted for ~45% of the mean concentration at Bermuda. At Barbados the variability of Se concentrations could not be explained solely by pollution sources. Correlations between Se and Sb, nitrate (NO3-), non-sea-salt sulfate (nssSO4=), and MSA were significant. The correlations of Se with Sb, NO3-, and nssSO4= suggested continental sources. The correlation with MSA indicated there was a significant marine biogenic source. Our results indicated that a marine biogenic source of Se accounted for 60--80% of the Se at Barbados. Analyses of seasonal relationships indicated that the marine biogenic source was most important during the summer. ¿ American Geophysical Union 1992