A method and apparatus for discarding a packet data convergence protocol (PDCP) service data unit (SDU) are disclosed. A PDCP layer sets a timer and discards a PDCP SDU upon expiration of the timer. The timer may be set upon receiving the PDCP SDU from an upper layer or upon submitting the PDCP SDU to a lower layer for transmission. The timer and a radio link control (RLC) discard timer may be coordinated. Alternatively, the PDCP layer may discard the PDCP SDU based on a notification from an RLC layer or based on a PDCP status report.