Hypocrellin　B　(HB)　was　encapsulated　into　a　phosphatidylcholine　liposome.　Encapsulation　of　HB　into　liposomes　not　only　improved　the　delivery　of　this　photosensitizer　but　also　increased　its　photodynamic　efficacy　compared　to　free　HB　molecules.　Liposomal　HB　showed　a　higher　cellular　uptake　than　free　HB　as　measured　by　confocal　microscopy　and　was　internalized　into　cultured　HeLa　cells　by　caveolar　endocytosis,　which　was　lipid-raft-dependent.　Cell　viability　measurements　demonstrated　that　liposomal　HB　was　more　phototoxic　to　HeLa　cells　than　free　HB　as　a　result　of　the　higher　concentration　of　intracellular　HB　delivered　by　the　liposomal　formulation.　The　encapsulation　of　HB　influenced　the　cell　death　pathway　by　an　increased　rate　of　necrotic　cells　after　irradiation　versus　free　HB,　and　a　Type　II　(singlet　oxygen)　mechanism　was　responsible　for　the　photocytotoxicity.