A method and wireless transmit/receive unit (WTRU) for enhanced uplink data transmission is disclosed. A transport block size for transmission of enhanced uplink data is selected. A medium access control (MAC) protocol data unit (PDU) is segmented into a plurality of segments on a condition that the MAC PDU does not fit in a transport block according to the selected transport block size. A transport block is produced having the transport block size and includes at least one of the plurality of segments. The transport block is transmitted over an enhanced uplink channel and an indication of the transport block size is transmitted over an associated physical control channel.