Autophagy　is　an　evolutionarily　conserved　pathway,　in　which　cytoplasmic　components　are　sequestered　within　double-membrane　vesicles　called　autophagosomes　and　then　transported　into　lysosomes　or　vacuoles　for　degradation.　Over　40　conserved　autophagy-related　(ATG)　genes　define　the　core　machinery　for　the　five　processes　of　autophagy:　initiation,　nucleation,　elongation,　closure,　and　fusion.　In　this　review,　we　focus　on　one　of　the　least　well-characterized　events　in　autophagy,　namely　the　closure　of　the　isolation　membrane/phagophore　to　form　the　sealed　autophagosome.　This　process　is　tightly　regulated　by　ESCRT　machinery,　ATG　proteins,　Rab　GTPase　and　Rab-related　proteins,　SNAREs,　sphingomyelin,　and　calcium.　We　summarize　recent　progress　in　the　regulation　of　autophagosome　closure　and　discuss　the　key　questions　remaining　to　be　addressed.