In this paper we report results of aircraft measurements of mass concentrations of carbonaceous aerosols, total aerosol mass, and simultaneously determined light scattering and absorption coefficients onshore and offshore of the eastern coast of the United States. We describe the sampling and analytical methodology used to derive spatially resolved aerosol carbon concentrations and discuss these in the context of other concurrently collected data. The carbon mass was, on average, 50% of the total dry aerosol mass. The carbon mass fraction tended to increase with altitude, suggesting that ground-based measurements can significantly underestimate the importance of carbon species in the column aerosol mass budget. The aerosol carbon mass was significantly correlated with aerosol light absorption, suggesting that the black and organic carbon components have, at least in part, common combustion sources. A regression of the light absorption coefficient onto carbon mass suggests that ~10% of the carbon mass is in the form of black (light-absorbing) carbon. ¿ 1997 American Geophysical Union