The properties of cluster ions and the processes in which they participate are examined. Information is given on the bond-dissociation energies of cluster ions. Processes that give rise to compound and cluster ions in ternary collisions, dissociative recombination of a cluster ion and an electron, and ion-molecule reactions involving cluster ions are studied, and the experimental rate constants are given for these processes. The processes that involve cluster ions in the upper atmosphere of the Earth are analyzed.