Method and apparatus for MAC in-order delivery are disclosed. The MAC in-order delivery may be activated per-connection and may be negotiated at connection setup. The MAC in-order delivery either for non-ARQ connections or ARQ connections may be performed by using HARQ packet ordering information. Alternatively, the MAC in-order delivery may be performed using a sequence number (SN) field at the MAC PDU level or using an SN field at the MAC SDU level. For a connection that has MAC in-order delivery disabled, the MAC PDU may not include an SN field, and an SN field may be included in a MAC extended header or a MAC sub-header when needed.