Methods for the generation of aerosols and vapors used in inhalation experiments were reviewed, and the characteristic features of the corresponding atmospheres and the limitations of the methods used to generate them were outlined. The toxicity of airborne particulates has been correlated with their characteristics, especially particle size and shape, chemical form, solubility, surface area, and the presence of carrier particles made of inert material. The control of these properties could determine the method used to produce the contaminant and the parameters used to characterize the atmosphere generated. The deposition of aerosol particles in the respiratory tract as a function of the aerodynamic diameter of the particle was examined, and the significance of the various aerosol characteristics was reviewed. Equipment used to generate aerosols were described, including compressed air nebulizers and ultrasonic nebulizers; devices used to pick up dust and aerosolize powders, such as the Deichman dust shaker, the dust aspirator, the dust feed scraper, and the fibrous aerosol generator; the Sinclair LaMer monodisperse aerosol generator; and the spinning disk aerosol generator. Models of electrostatic precipitators were presented, and methods for measuring the concentrations of vapors at various sites including the breathing zone of test animals were reviewed. Sampling for monitoring exposure atmospheres was also discussed.