In this paper we describe the polyamine biosynthesis and oxidation processes, giving an overview about recent results in free-living Amoebae. The protozoa polyamine levels are different in comparison with mammalian cells. Also, the polyamine levels in protozoa cells change if these species are pathological or not for the human beings. All the amoeba strains show high concentrations of 1,3-diaminopropane (DAP), spermidine and acetylspermidine while spermine is absent. In these amoeba a considerable polyamine oxidase activity has been found, which acts on N8-acetylspermidine, but not on free polyamines. This enzyme is responsible, together with polyamine acetylase, of DAP synthesis whose function is not well known.