The vertical distribution of stratospheric particles with an average radius of 0.15 micron is presented in the form of five vertical profiles. These show a broad maximum in numerical concentration between 15 and 23 km, and are remarkably consistent throughout the one-year period of observations from November, 1959 to October, 1960. It is suggested that this “aerosol layer” is identical to the particles responsible for the “purple light” phenomenon, and the haze layers observed in the stratosphere. Some pertinent details of the balloon-borne collection instruments are included. Abstract The vertical distribution of stratospheric particles with an average radius of 0.15 micron is presented in the form of five vertical profiles. These show a broad maximum in numerical concentration between 15 and 23 km, and are remarkably consistent throughout the one-year period of observations from November, 1959 to October, 1960. It is suggested that this “aerosol layer” is identical to the particles responsible for the “purple light” phenomenon, and the haze layers observed in the stratosphere. Some pertinent details of the balloon-borne collection instruments are included.