Environment is characterized by a significant number of physical parameters, among which is the air ionization. It is also important under biomedical aspect, because it exercises the beneficial influences of living organisms. In the introductory considerations, the paper presents some theoretical details of how air ions are generated naturally and are mentioned some biological effects produced by ions (especially by artificial ionization), the most important from therapeutically point of view. Then, are presented the measurement methods of this electrical component of the ambient air and some ion concentrations from different places, but also in some balneary-climatic resorts from Romania. In the final part of the paper are mentioned the conclusions, as well as some new possible explanations (based on quantum theory) on how the air ions act on living organisms.