This paper describes a program of aerosol measurements made in the fall of 1965 at Cape Blanco and Crater Lake, Ore. Aerosol size distributions were determined with a Royco light-scattering type particle counter and with condensation nuclei counters. Size distributions at Crater Lake (2200 m altitude) were found to be well approximated by power law distributions with exponents between 3 and 4. The Cape Blanco data agree well with earlier measurements of sea-spray, aerosol size distributions. A Goetz aerosol centrifuge was used, in conjunction with filter sampling, to determine the size distribution of the chloride- and sulfur-compound fractions of the aerosol. At Crater Lake, sulfur-to-chloride ratios of about 8 were observed and considerable concentrations of other materials could be inferred. The data indicate that significant amounts of sea-spray aerosol did not penetrate upward to altitudes >2000 m. The aerosols identified with these 2000 m tropospheric levels are believed to be aged aerosols from continental sources. High-altitude tropospheric aerosols were also observed at Crater Lake during periods of subsidence; their concentrations were lower than those found under other synoptic weather conditions. The power law representations for subsidence aerosols had lower exponential values than those for the lower altitude tropospheric aerosols.