Primary defined as the cellular receptors for immunosuppressive drugs, the immunophilins encompass two ubiquitous protein families. They consist of the FK506 binding proteins termed as FKBPs and cyclosporin binding proteins referred to as cyclophilins. They have been found in all orga- nisms. The 52 genes encode immunophilins have been identified in A. thaliana genome, among which 23 encode putative FKBP and 29 putative cyclophilins. Despite the various structure both families have peptidyl-prolyl cis/trans isomerase (PPIase) activity. Whilst the role of FKBPs and cyclophilin in pro- teins maturation is well understanding, the current stage of knowledge of different functions of this ubi- quitous protein family in plant cell is poor. As a significant component of the chloroplast proteome, immunophilins may play important roles in processes which take place in this subcellular compartment. Moreover, evidence for the role of multidomain immunophilins in plant growth and development comes from characterization of mutants showing very marked developmental abnormalities.