A method and wireless transmit/receive unit (WTRU) for supporting enhanced uplink (EU) transmissions are disclosed. A WTRU is configured to provide hybrid automatic repeat request (H-ARQ) processes for supporting transmission over an enhanced uplink (EU) channel, to receive configuration information, wherein the configuration information indicates which H-ARQ processes are associated with a particular MAC-d flow, to allocate an H-ARQ process for transmission of data from the MAC-d flow, wherein the allocated H-ARQ process is from one of the associated H-ARQ processes, and to transmit data from the MAC-d flow over the EU channel using the allocated H-ARQ process.