Mitochondria play an essential role in eukaryotic cells, supplying energy levels which vastly exceed those available to prokaryotes. They rely heavily on the import of nuclear encoded proteins for their function. The FAST family of proteins which are synthesized in the cytoplasm and imported into mitochondria are an example of this. The FAST family has not been well characterized, and next to nothing is known about several FAST family members. In the following I have reviewed what is known about each member of the FAST protein family including conserved domains, structures, including roles in cellular function, apoptosis and disease. Additionally, our lab has begun to characterize FASTKD4, one of the least studied FAST family members. We have determined that FASTKD4 is both a cytoplasmic and a mitochondrial protein, it does not reside in the outer mitochondrial membrane, its overexpression is not acutely toxic, and preliminary results suggest that it is not a member of any large complex in resting cells.