The results of spectral aerosol optical depth measurements in the Pacific Ocean and in the North Atlantic are presented. Comparisons of aerosol optical depth spectra indicate that the optical properties of the maritime aerosols influencing Pacific Ocean measurements are substantially different than those of the North Atlantic data. The values of the Angstrom parameter calculated in the 461- to 1016-nm range for the Pacific Ocean data are about a factor of 2 less than those for the North Atlantic. For the Pacific Ocean data an increase in optical depth with increasing wavelength in the 1016- to 1640-nm range is attributed to a narrow mode coarse size distribution. This mode is found to be substantially independent of the fine mode variability. In contrast the fine and coarse modes are well correlated for the North Atlantic data. ¿ American Geophysical Union 1994