A tissue-removing catheter configured for insertion into a body lumen of a subject, the catheter comprising: a drive shaft having opposite proximal and distal end portions (12a, 12b), and longitudinal axis extending between the proximal and distal end portions thereof; a tissue-removing element operatively connected to the distal end portion of the drive shaft such that rotation of the drive shaft imparts rotation of the tissue-removing element; and a drive assembly (20, 120) operatively connected to the proximal end portion of the drive shaft, characterised in that the drive assembly comprises: a prime mover (40, 140) configured to generate a rotational drive force; and a reciprocating rotor (44, 144) operatively connected to the prime mover to receive the rotational drive force, the reciprocating rotor configured to simultaneously rotate about a rotor axis and reciprocate along the rotor axis in response to the rotational drive force, the reciprocating rotor being operatively connected to the proximal end portion of the drive shaft to impart rotation to the drive shaft about the longitudinal axis and reciprocation of the drive shaft along the longitudinal axis as the rotor rotates and reciprocates relative to the rotor axis, wherein the drive assembly further comprises a stator comprising a bearing projection (56, 58) configured to constrain rotation and reciprocation of the reciprocating rotor relative to the rotor axis, wherein the rotor defines a race extending around the rotor axis, wherein the bearing projection is received in the race and wherein the race defines an axially sinuous path as the groove extends around the rotor axis, and wherein the drive assembly is cannulated. a drive shaft having opposite proximal and distal end portions (12a, 12b), and longitudinal axis extending between the proximal and distal end portions thereof; a tissue-removing element operatively connected to the distal end portion of the drive shaft such that rotation of the drive shaft imparts rotation of the tissue-removing element; and a drive assembly (20, 120) operatively connected to the proximal end portion of the drive shaft, characterised in that the drive assembly comprises: a prime mover (40, 140) configured to generate a rotational drive force; and a reciprocating rotor (44, 144) operatively connected to the prime mover to receive the rotational drive force, the reciprocating rotor configured to simultaneously rotate about a rotor axis and reciprocate along the rotor axis in response to the rotational drive force, the reciprocating rotor being operatively connected to the proximal end portion of the drive shaft to impart rotation to the drive shaft about the longitudinal axis and reciprocation of the drive shaft along the longitudinal axis as the rotor rotates and reciprocates relative to the rotor axis, wherein the drive assembly further comprises a stator comprising a bearing projection (56, 58) configured to constrain rotation and reciprocation of the reciprocating rotor relative to the rotor axis, wherein the rotor defines a race extending around the rotor axis, wherein the bearing projection is received in the race and wherein the race defines an axially sinuous path as the groove extends around the rotor axis, and wherein the drive assembly is cannulated. a prime mover (40, 140) configured to generate a rotational drive force; and a reciprocating rotor (44, 144) operatively connected to the prime mover to receive the rotational drive force, the reciprocating rotor configured to simultaneously rotate about a rotor axis and reciprocate along the rotor axis in response to the rotational drive force, the reciprocating rotor being operatively connected to the proximal end portion of the drive shaft to impart rotation to the drive shaft about the longitudinal axis and reciprocation of the drive shaft along the longitudinal axis as the rotor rotates and reciprocates relative to the rotor axis, wherein the drive assembly further comprises a stator comprising a bearing projection (56, 58) configured to constrain rotation and reciprocation of the reciprocating rotor relative to the rotor axis, wherein the rotor defines a race extending around the rotor axis, wherein the bearing projection is received in the race and wherein the race defines an axially sinuous path as the groove extends around the rotor axis, and wherein the drive assembly is cannulated.