A method and apparatus for processing multiple-input multiple-output (MIMO) transmission are disclosed. A wireless transmit/receive unit (WTRU) receives downlink control information including WTRU-specific MIMO and transport format information and MIMO information for all other WTRUs assigned to the same resource. The WTRU processes received MIMO data based on the downlink control information. The downlink control information may also include transport format information for all other WTRUs assigned to the same RB. The downlink control information may be transmitted via WTRU-specific control signaling. All WTRUs' MIMO and/or transport format information may be transmitted via resource-specific common control signaling. The downlink control signaling format may include at least one of a number of streams for the WTRU, a number of active WTRUs assigned to the same resource, a spatial channel identity for the WTRU, a MIMO mode, a precoding matrix index and a precoding vector index.