A tissue resecting instrument, comprising: a housing defining an interior; a shaft (130; 530; 630; 730) rotatable relative to the housing and extending distally from the housing, the shaft (130; 530; 630; 730) defining a proximal end portion disposed within the interior of the housing, a distal end portion distally-spaced from the housing, and a lumen extending therethrough, the lumen disposed in fluid communication with the interior of the housing; a cutting member (140; 540; 640; 740) operably associated with the distal end portion of the shaft (130; 530; 630; 730) to enable tissue resection upon rotation of the shaft (130; 530; 630; 730); a turbine (152; 852; 952) disposed within the interior of the housing and operably associated with the proximal end portion of the shaft (130; 530; 630; 730) such that rotation of the turbine (152; 852; 952) rotates the shaft (130; 530; 630; 730) relative to the housing to thereby rotate the cutting member (140; 540; 640; 740), the turbine (152; 852; 952) including a plurality of fins (158; 858; 958); and a fluid outflow tube operably associated with the housing, the fluid outflow tube adapted to connect to a suction source to enable the suctioning of fluid and resected tissue proximally through the lumen of the shaft (130; 530; 630; 730), the interior of the housing, and into the fluid outflow tube, characterised in that the lumen of the shaft (130; 530; 630; 730) communicates with the housing through a plurality of openings defined through the shaft (130; 530; 630; 730) towards the proximal end portion thereof such that proximal fluid flow flows from an operative site, through the lumen, into the housing through the openings, and across the plurality of fins (158; 858; 958) of the turbine (152; 852; 952) to urge the turbine (152; 852; 952) to rotate, thereby rotating the shaft (130; 530; 630; 730) relative to the housing to enable tissue resection with the cutting member (140; 540; 640; 740). a housing defining an interior; a shaft (130; 530; 630; 730) rotatable relative to the housing and extending distally from the housing, the shaft (130; 530; 630; 730) defining a proximal end portion disposed within the interior of the housing, a distal end portion distally-spaced from the housing, and a lumen extending therethrough, the lumen disposed in fluid communication with the interior of the housing; a cutting member (140; 540; 640; 740) operably associated with the distal end portion of the shaft (130; 530; 630; 730) to enable tissue resection upon rotation of the shaft (130; 530; 630; 730); a turbine (152; 852; 952) disposed within the interior of the housing and operably associated with the proximal end portion of the shaft (130; 530; 630; 730) such that rotation of the turbine (152; 852; 952) rotates the shaft (130; 530; 630; 730) relative to the housing to thereby rotate the cutting member (140; 540; 640; 740), the turbine (152; 852; 952) including a plurality of fins (158; 858; 958); and a fluid outflow tube operably associated with the housing, the fluid outflow tube adapted to connect to a suction source to enable the suctioning of fluid and resected tissue proximally through the lumen of the shaft (130; 530; 630; 730), the interior of the housing, and into the fluid outflow tube, characterised in that the lumen of the shaft (130; 530; 630; 730) communicates with the housing through a plurality of openings defined through the shaft (130; 530; 630; 730) towards the proximal end portion thereof such that proximal fluid flow flows from an operative site, through the lumen, into the housing through the openings, and across the plurality of fins (158; 858; 958) of the turbine (152; 852; 952) to urge the turbine (152; 852; 952) to rotate, thereby rotating the shaft (130; 530; 630; 730) relative to the housing to enable tissue resection with the cutting member (140; 540; 640; 740).