Abstract: There is described an adjustable dose injection pistol comprising a body assembly (1) including an elongate chamber (8), a piston chamber (3) including a piston (13) slideable in the chamber (8) between filled and discharged positions and means for adjusting (16, 26, 19, 20, 22, 23) one of said positions.The means comprise a selectable plurality of channels (20, 22, 23) included in one of the assemblies (1, 3), the channels (20, 22, 23) being spaced about and parallel to the piston-chamber axis, and an arrestor (19) located on the other assembly (1, 3), the arrestor (19) being selectably engageable with an aligned channel (20, 22, 23) upon movement of said piston (13) between said positions.The channels (20, 22, 23) are preferably located in the piston assembly (3) on a sleeve (16) concentrically mounted with the piston (13) and rotable with respect to the chamber (8).The pistol may be used for the injection of liquids into animals.