The present invention relates to a drive mechanism of a drug delivery device for dispensing of dose of a medicament, the mechanism comprising: &mdashan elongated housing (30) extending in an axial direction (1, 2), &mdasha piston rod (80) to operably engage with a piston (16) of a cartridge (14) to displace the piston (16) in a distal axial direction (1), &mdasha drive sleeve (50) extending in axial direction (1, 2) and being rotatable against the action of a spring (68) during a dose setting procedure, &mdasha dispensing sleeve (70) rotatably engaged with the piston rod (80) and being displaceable in axial direction (1, 2) relative to the drive sleeve (50) to engage with the drive sleeve (50) in a torque transmissive way during a dose dispensing procedure.
