Tail-anchored (TA) proteins are a unique class of functionally diverse membrane proteins that are defined by their single C-terminal transmembrane domain and their ability to insert post-translationally into specific organelles in an Ncytosol-CIMS orientation. While in recent years considerable progress has been made towards understanding the biogenesis of TA proteins in yeast and mammals, relatively little is known about how these proteins are properly partitioned within plant cells, mostly because so few plant TA proteins have been identified. Here we show the results of experiments aimed at cataloguing, in silico, all of the TA outer mitochondrial membrane and plastid outer envelope proteins in Arabidopsis and then identifying and characterising distinct, C-terminal targeting motifs responsible for the proper sorting of at least a subset of these proteins. Collectively, the results of this thesis provide important insight into the molecular mechanisms that underlie the biogenesis of TA proteins in plant cells.