More than 80 hours of airborne cloud condensation nuclei (CCN) measurements made during the first phase of the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE 1) in the northeast Pacific and the Atlantic Stratocumulus Transition Experiment (ASTEX) in the northeast Atlantic are presented and analyzed. The complete CCN spectra from 0.6% to 0.02% supersaturation and condensation nuclei concentrations are presented. Substantial direct continental/anthropogenic influence in ASTEX resulted in an obvious division into maritime and continental components, which had 5 times higher concentrations. Boundary layer FIRE 1, ASTEX maritime, and previously published summertime Southern Ocean number concentration measurements with the same instrument were comparable (110, 197, and 165 cm-3, respectively, at 0.6% supersaturation; 45, 60, and 48 cm-3 at 0.1% supersaturation, and 18, 19, and 20 cm-3 at 0.02% supersaturation). ¿ 1999 American Geophysical Union