Programmable logic devices (PLDs) that can be repeatedly erased and reprogrammed, e.g., during the testing and/or design phases, and then converted to one-time programmable (OTP) devices on a permanent basis, and methods of converting a PLD to an OTP device. In some embodiments, only the erase function is disabled in the device. Because programming data cannot then be erased from the device, the addition of new programming data is very unlikely to yield an operable design. Therefore, the programming function is also effectively disabled. The programming function can be directly disabled in addition to or instead of the erase function, if desired. The erase and/or programming functions can be disabled, for example, by blowing one or more fuses included in the erase and/or programming circuitry of the PLD.