A medicament delivery device (10) comprises a medicament delivery mechanism including an injection needle (23). A housing (11) contains at least one component of the medicament delivery mechanism. A base plate (12) includes a contact surface (12b) for placement against a patient's body. The housing (11) is moveably connected to the base plate (12) and is moveable relative to the base plate (12) between a first position and a second position. The medicament delivery mechanism is operative upon movement of the housing (11) from the first position to the second position.