A medicament delivery device (1) comprises a housing (2) for holding a medicament cartridge (9), a piston rod (22, 24) and a drive (11, 20). The medicament cartridge (9) has a medicament outlet and a bung (13) moveable axially along the medicament cartridge for dispensing a medicament, the piston rod has a plunger (24) for moving the bung and a lead member (22) telescopically coupled to the plunger (24) that may be driven by the drive (11, 20) to extend or retract the piston rod (22, 24). Additionally, the device comprises a linkage (40) coupled between the plunger (24) and an anchorage (44) and a drive member (20) telescopically coupled to the lead member (22). The drive (11) is operative to rotate the drive member (20) to telescopically move the lead member relative to the drive member whereby the plunger is moved relative to the lead member by way of the linkage (40).
