Radioactive aerosols are a substantial risk factor in radiation safety in the atomic industry, mining industry, nuclear warhead depository and nuclear waste storage, as well as the natural radioactivity in houses. Assessment of the exposure, dose and health effect is very important for workers and the general population.  In the last 5-10 years the problem of dosimetry of non-radioactive aerosols has become a "hot" topic in environmental health science with emphasis on submicron and even nanometer-sized particles. Both radioactive and non-radioactive aerosols are subject to a problem of uncertainty in the dose assessment, because of the contact between the human respiratory system and unstable medium - aerosols.  Radioactive aerosols data will be presented based Dr. Ruzer's book, "Radioactive Aerosols," recently published in Russia. For non-radioactive aerosols a review will be presented of recent publications related to aerosol exposure and dose assessment with a discussion of the special role of nanometer-sized particles.