An injection device for holding and activating a two-chamber ampulla has components whose relative movement causes the pistons of the two-chamber ampulla to be moved in order to mix the substances, as well as devices for injecting the product which is mixed in this way. For this purpose, a receptacle (103) into which the two-chamber ampulla (111) can be inserted and secured is held in a housing (101), and the receptacle (103) can be displaced by means of a carriage (108). A tappet (104) which acts on the pistons (111A, 111B) is movably held in the receptacle (103). A traction cable (114) which is deflected by means of a roller (109) which is mounted on the carriage (108) and one of whose ends is connected to the receptacle (103) and the other end of which is connected to a tension spring (110) which is held on the housing (101) is provided in order to carry out a mixing stroke, insertion stroke, injection stroke and a return stroke. Devices which can be activated automatically and/or manually between the housing (101), receptacle (103), tappet (104) and carriage (108) control their alternating coupling to the traction cable (114) and thus the sequence of the mixing stroke, insertion stroke, injection stroke and return stroke. The invention thus provides a partially automatic injection device for two-chamber ampullas whose handling comfort and safety for the patient are substantially improved.