A method and apparatus for quickly masking defective memory elements with substitute memory elements includes first and second memory blocks. The first memory block includes a first memory array and a second spare memory array. The second memory block includes a second memory array and a first spare memory array. A first word from the first memory array is selected concurrently with a first substitute word from the first spare memory. An address signal is decoded and then compared with data representative of a defective word. In the event it is determined, as a result of this comparison, that the first word is defective, the first substitute word is then communicated to a common data bus. Alternatively, the first word is communicated to the common data bus.