Techniques for sending feedback information for multi-carrier operation are described. In an aspect, feedback information may be sent on an uplink carrier that may or may not be paired with a downlink carrier on which data transmission is sent. A user equipment (UE) may receive data transmission on a downlink carrier among a plurality of downlink carriers. The UE may determine feedback information for the data transmission, determine an uplink carrier to use to send the feedback information from among a plurality of uplink carriers, and send the feedback information on the uplink carrier. In another aspect, feedback information for multiple downlink carriers may be sent on at least one uplink carrier using Single-Carrier Frequency Division Multiple Access (SC-FDMA). A UE may receive data transmissions on a plurality of downlink carriers, determine feedback information for the data transmissions, and send the feedback information on at least one uplink carrier using SC-FDMA.