pHs were measured in minimally diluted extracts of size-segregated aerosols sampled under moderately polluted conditions at Bermuda during spring 1997. Extrapolation to aerosol liquid water contents yielded ambient pHs for most super-¿m diameter size fractions in the upper 3s to upper 4s. Aerosols within this size range of each sample approached similar pH. These results are consistent with recent estimates of sea-salt aerosol pHs based on thermodynamic considerations and model calculations. Most pHs for finer aerosol size fractions were in the 1s and 2s. The H+ + SO42- ↔ HSO4- equilibrium strongly buffered aerosol pH in all size fractions.