A computer-controlled injector of the type having a motor which advances and retracts a plunger located within a syringe housing toward and away from a nozzle located in the front of the syringe to inject fluid into or out of an animal subject. The injector includes a display for querying the operator as to operating parameters for an injection, such as the capacity of the syringe, prior to an injection. The injector may be configured so as to generate a different sequences of displays prior to an injection, e.g., to not include a query as to the syringe capacity if the injector will not be used with syringes of differing capacities.