Power control for devices having multiple transmit antennas are disclosed, including power control methods for Physical Uplink Control Channel (PUCCH) and Sounding Reference Signal (SRS) transmissions for a wireless transmit/receive unit (WTRU). The PUCCH and SRS power control methods include selecting a multiple input multiple output (MIMO) mode and changing the power of the PUCCH or SRS transmission based on the selected MIMO mode. Another power control method estimates an antenna gain imbalance (AGI) for a WTRU having at least two transmit antennas. The AGI is based on measuring a Reference Signal Received Power (RSRP) on each transmit antenna. Each transmit antenna is then scaled by an AGI scaling factor based on the estimated AGI.