Air microbial sampling is a subject of great interest in different fields of human activity; however, generally accepted indications, concerning both the sampling methods to be used and the interpretation of the results, are still lacking. The whole theme is greatly debated and several problems remains to be solved. The aim of this article is to provide knowledge relating to the problems associated with air microbial sampling, underlining the aspects to be considered in order to choice the sampling method on the basis of the objective of the sampling itself and on the knowledge of the characteristics and limits of the different methods.