The　anisotropy　of　cleavage　fracture　stress　and　its　relationship　to　thermomechanical　processing　(TMP)　and　microstructure　has　been　determined　by　extensive　study　on　a　Nb,　Ti　microalloyed　line　pipe　steel.　127　mm-thick　pieces　cut　from　a　commercially　cast　slab　were　reduced　to　a　25　mm-thick　plate　by　three　different　rolling　schedules.　The　final　microstructures　of　the　rolled　plate　were　various　combinations　of　polygonal　ferrite,　bainite　and　deformed　ferrite,　having　a　range　of　grain　sizes.　Four-point　bend　tests　(L-T,　L-S,　T-L　orientations),　compact　tension　tests　(S-L　orientation)　and　tensile　tests　(L,　T,　S　orientations)　were　carried　out　at　-196　degrees　C　for　each　rolling　schedule.　An　elastic-plastic　finite　element　method　was　used　to　calculate　the　stress　and　strain　distributions　ahead　of　the　notches　for　the　various　orientations.　By　measuring　the　distance　of　the　cleavage　fracture　initiation　site　from　the　root　of　the　notch,　the　cleavage　fracture　stress　was　determined　for　each　orientation.　The　results　show　a　significant　variation　in　cleavage　fracture　stress　with　orientation　and　TMP　treatment.　The　anisotropy　of　cleavage　fracture　stress　increases　with　decreasing　finish-rolling　temperature　(FRT),　the　S-L　orientation　generally　giving　the　minimum　value.　The　TMP　treatment　which　produces　unrecrystallized　austenite　at　the　FRT　has　the　best　combination　of　high　cleavage　fracture　stress　and　low　anisotropy.　(C)　2000　Elsevier　Science　Ltd.　All　rights　reserved.