Abstract: A system and method is provided for selectively injecting interrupts within the instruction stream of a data processing system. The system includes a programmable storage device for storing interrupt injection signals, each of which is associated with a respective machine instruction. When execution of the associated machine instruction is initiated, the stored signal is read from the storage device and is made available to the interrupt logic within the instruction processor. If set to a predetermined logic level, the signal causes an interrupt to be injected within the instruction processor. The system provides the capability to simultaneously inject different types of interrupts, including fault and non-fault interrupts, during the execution of any instruction. The invention further provides a programmable means for injecting errors at predetermined intervals in the instruction stream.