The　multi-modes　and　disperse　characteristics　of　torsional　modes　in　pipes　are　investigated　theoretically　and　experimentally.　At　all　frequencies,　both　phase　velocity　and　group　velocity　of　the　lowest　torsional　mode　T(0,1)　are　constant　and　equal　to　shear　wave　velocity.　T(0,1)　mode　at　all　frequencies　is　the　fastest　torsional　mode.　In　the　experiments,　T(0,1)　mode　is　excited　and　received　in　pipes　using　9　thickness　shear　vibration　mode　piezoelectric　ceramic　elements.　Furthermore,　an　artificial　longitudinal　defect　of　a　4　m　long　pipe　is　detected　using　T(0,1)　mode　at　50　kHz.　Experimental　results　show　that　it　is　feasible　for　longitudinal　defect　detection　in　pipes　using　T(0,1)　mode　of　ultrasonic　guided　waves.