A method and apparatus for acknowledge mode data (AMD) re-segmentation are disclosed. An AMD protocol data unit (PDU) is generated from at least one RLC SDU. The AMD PDU size is within a flexible maximum AMD PDU size. The original AMD PDU is stored in a retransmission buffer, and transmitted. If transmission of the original AMD PDU fails and the original AMD PDU size is larger than an updated maximum AMD PDU size, the original AMD PDU is segmented to segmented AMD PDUs. If transmission of one of the segmented AMD PDUs fails, the original AMD PDU may be re-segmented to smaller size AMD PDUs.