A medicament delivery device (100) for delivery of medicament from a cartridge (10) into an injection site, through a cannula (134). The cartridge has a medicament chamber (14) with an outlet (15), and a sealing element (16) for closing the outlet (15). The device has a housing (102) for receiving the cartridge (10), and a drive mechanism (200) to expel the medicament from the device upon activation of the drive mechanism (200). The device has a connection arrangement (199) comprising a hub (166) and spring means (184) for driving relative movement between the hub (166) and the cartridge (10) upon operation of an operating member (190). The operating member switches the connection arrangement (199) from an unconnected configuration to a connected configuration, in which the hub (166) cooperates with the cartridge (10) to open the outlet (15). When connected, fluid may flow between the chamber (14) and the cannula (134).