Filamentous bacteriophages, also known as filamentous bacterial viruses or Inoviruses, have been studied extensively over the years. They are interesting paradigms in structural molecular biology and offer insight into molecular assembly, a process that remains to be fully understood. In this chapter, an overview on filamentous bacteriophages will be provided. In particular, we review the constituent proteins of filamentous bacteriophage and discuss assembly by examining the structure of the major coat protein at various stages of the process. The minor coat proteins will also be briefly reviewed. Structural information provides key snapshots into the dynamic process of assembly.