The　traditionally　used　cylindroid　guided　wave　modes　are　not　suitable　for　the　detection　of　limited　circumferential　extent　defects　and　the　evaluation　of　the　axial　extent　of　defects　within　a　pipe.　The　reason　is　that　it　is　difficult　to　generate　reflections　from　limited　circumferential　extent　defects　using　traditional　modes.　It　is　also　difficult　to　evaluate　the　axial　extent　of　defects　by　using　them.　This　article　proposes　using　the　spirally　propagating　circumferential　Lamb　(CL)　wave　triggered　by　a　specially　designed　circumferential　Lamb　wave-based　magnetostrictive　patch　transducer　(CL-MPT).　It　can　rapidly　detect　the　position　of　a　defect　regardless　of　its　limited　circumferential　extent,　rather　than　the　axial　scanning　of　pipes　using　traditional　circumferential　modes.　The　axial　extent　of　a　defect　can　also　be　evaluated　by　summating　the　number　of　the　signals　that　contain　defect　reflections.　It　was　experimentally　proven　that　the　CL　wave　could　be　applied　to　supplement　the　traditional　modes.　©　1963-2012　IEEE.