The lifespan of organisms is generally considered to be partially under genetic control. Changes in the genetic apparatus and/or in the flow of genetic information to proteins, therefore, could be one of the mechanisms involved in the aging process. Several theories of aging exist, that include the role of protein synthesis. Furthermore, indications have been obtained for the existence of correlations of functional loss of some organs with alterations in protein levels. Aging and protein synthesis have been studied extensively and in most cases the liver has been chosen to examine this process. The obtained results, however, are often contradictory and, therefore, the relationship aging--protein synthesis is still not clear. This article will give an overview of these studies and will discuss the various steps in the protein synthesising machinery: RNA synthesis, mRNA levels and translation. In addition, the possible causes of the variability in the experimental results will be briefly discussed.