A first report is presented on a comprehensive study of stratospheric aerosols up to 30 km altitude. Information was obtained on the vertical profiles as a function of particle size, on the size distribution of these particles and on their physical structure and chemical composition. Vertical concentration profiles are first considered theoretically on the basis of equilibria between eddy diffusion, sedimentation, subsidence and coagulation. The results are compared with two sets of data: (1) vertical profiles obtained with a recording Aitken nuclei counter which measures the size range of 0.01 to 0.1 microns radius and (2) vertical profiles obtained with impactors over the size range of 0.1 to 1.0 microns radius. The first of these indicates a decrease in concentration from the tropopause to nearly zero at 20 km, whereas the second shows a maximum at about 20 km. The size distributions of these particles were found to be quite constant with time. There is a maximum between 0.01 and 0.1 μ radius,... Abstract A first report is presented on a comprehensive study of stratospheric aerosols up to 30 km altitude. Information was obtained on the vertical profiles as a function of particle size, on the size distribution of these particles and on their physical structure and chemical composition. Vertical concentration profiles are first considered theoretically on the basis of equilibria between eddy diffusion, sedimentation, subsidence and coagulation. The results are compared with two sets of data: (1) vertical profiles obtained with a recording Aitken nuclei counter which measures the size range of 0.01 to 0.1 microns radius and (2) vertical profiles obtained with impactors over the size range of 0.1 to 1.0 microns radius. The first of these indicates a decrease in concentration from the tropopause to nearly zero at 20 km, whereas the second shows a maximum at about 20 km. The size distributions of these particles were found to be quite constant with time. There is a maximum between 0.01 and 0.1 μ radius,...