An autoinjector comprising an outer housing in which is mounted a syringe comprising a barrel for holding a volume of medicament, a needle at one end of the barrel and a plunger axially-moveable in the barrel, the autoinjector further comprising an inner housing intermediate the outer housing and the syringe and an energy source in communication with said inner housing, wherein the inner housing is moveable by the energy source between three positions, namely a first position in which the inner housing is in communication with the barrel, the plunger and barrel being moveable axially so as to move at least part of said needle out of the outer housing; a second position in which the inner housing is in communication with the plunger but not the barrel, said plunger being moveable axially into said barrel so as to expel medicament through the needle; and a third position in which the inner housing is in communication with neither the plunger nor the barrel, the plunger and barrel being retractable to retract the needle into the outer housing, characterised in that the autoinjector further comprises means associated with a rear flange of said plunger providing a plurality of axial positions at which it is possible for said inner housing to engage said plunger in said second position. a barrel for holding a volume of medicament, a needle at one end of the barrel and a plunger axially-moveable in the barrel, the autoinjector further comprising an inner housing intermediate the outer housing and the syringe and an energy source in communication with said inner housing, wherein the inner housing is moveable by the energy source between three positions, namely a first position in which the inner housing is in communication with the barrel, the plunger and barrel being moveable axially so as to move at least part of said needle out of the outer housing; a second position in which the inner housing is in communication with the plunger but not the barrel, said plunger being moveable axially into said barrel so as to expel medicament through the needle; and a third position in which the inner housing is in communication with neither the plunger nor the barrel, the plunger and barrel being retractable to retract the needle into the outer housing, characterised in that the autoinjector further comprises means associated with a rear flange of said plunger providing a plurality of axial positions at which it is possible for said inner housing to engage said plunger in said second position. a first position in which the inner housing is in communication with the barrel, the plunger and barrel being moveable axially so as to move at least part of said needle out of the outer housing; a second position in which the inner housing is in communication with the plunger but not the barrel, said plunger being moveable axially into said barrel so as to expel medicament through the needle; and a third position in which the inner housing is in communication with neither the plunger nor the barrel, the plunger and barrel being retractable to retract the needle into the outer housing, characterised in that the autoinjector further comprises means associated with a rear flange of said plunger providing a plurality of axial positions at which it is possible for said inner housing to engage said plunger in said second position.