A method and an apparatus for utilizing multiple carriers are disclosed. A wireless transmit/receive unit (WTRU) capable of receiving on a single downlink carrier at a time may tune the receiver to one downlink carrier and switch the downlink carrier in accordance with a configured pattern. The WTRU may switch the carrier from an anchor carrier to a non-anchor carrier at a high speed shared control channel (HS-SCCH) sub-frame boundary, and switches back at an end of a subsequent high speed physical downlink shared channel (HS-PDSCH) subframe. The WTRU may switch the carrier at an HS-PDSCH sub-frame boundary. A WTRU capable of receiving on multiple downlink carriers simultaneously may tune the receiver to an anchor carrier and a supplementary carrier, and switch the supplementary carrier to another carrier based on a carrier switching order. The carrier switching order may be received via an HS-SCCH or via layer 2 signaling.