An angiographic injector has an injector portion which includes a rotating turret for housing two angiographic syringes in readiness for injection. The injector further employs a driving mechanism for connecting with and controlling the movement of a syringe plunger once one of the syringes is in place for injection. Through the use of guide means on each syringe and corresponding alignment means on a pressure jacket, the syringe is alignably and securely mounted within the pressure jacket on the rotating turret. Each syringe plunger is releasably connected to the driving mechanism for an injection operation, and released from the driving mechanism when the injection operation has been completed, such that the driving mechanism can be withdrawn from the syringe relative to the plunger without drawing body fluid of a patient into the syringe. Various types of plunger release mechanisms for this purpose are disclosed.