Aerosols from the marine boundary layer were collected during a cruise form the Peru/Ecuador shelf through the equatorial and tropical Pacific to the Hawaiian Islands. A variety of samplers of different design and independent analytical techniques were used to validate the results obtained. On large particles, little or no chloride deficiency relative to seawater composition was observed, while on submicrometer particles, as much as 40% of chloride had been lost. A silicate component with a composition similar to the crustal average was associated with sea-salt particles as an internal mixture. Along the Peru coast, substantial concentrations of Cu, Zn, As, and Pb were found which must be related to large emissions from the metallurgical industry in that region. High levels of selenium in the remote equatorial region suggest a biological source of volatile selenium in this area of high productivity. The concentrations of excess sulfate were found to be consistent with the flux of dimethylsulfide determined on the same cruise. The presence of soot carbon, particulate organic carbon, and fine excess potassium showed evidence of long-range transport of combustion-derived aerosols to this remote region. Enhanced soot and crustal elements in the Intertropical Convergence Zone suggest downward mixing of materials transported in the upper troposphere in this region of active vertical exchange.