Data verification methods and/or nonvolatile memory devices are provided that concurrently detect data for a selected memory cell of the nonvolatile memory device and verify a programmed or erase state of previously detected data of a different memory cell of the nonvolatile memory device. Concurrently detecting data and verifying a programmed or erase state may be provided by a sense amplifier configured to sense data from a memory cell of the nonvolatile memory device, a latch configured to store the data sensed by the sense amplifier, an I/O buffer configured to store the data stored in the latch and a program/erase verifier circuit configured to control the sense amplifier, latch and I/O buffer to provided previously sensed data for a first memory cell to the program erase/verifier circuit for verification while the sense amplifier is sensing data for a second memory cell.