Size fractions of inland aerosols collected by cascade impactor have been analyzed for Cl and Br by neutron activation. Br mass often shows an approximately inverse radius dependence with impactor size range, corresponding to a distribution proportional to total surface area of particles in each size range. A decrease in abundance observed in the intermediate‐sized fractions, as compared with smaller particles, during precipitation is interpreted as reflecting the lower size limit for particles nucleating cloud droplets or crystals. The low ratio of Br to Cl found in larger particles and precipitation, as compared with smaller particles, suggests that Cl‐rich particles are activated and removed from the atmosphere by precipitation more efficiently than Br‐rich particles.