We study the problem of establishing rendezvous between two secondary users. We assume that each user has two radios that can be used concurrently. We present the bidirectional algorithm that exploits the two radios. Assuming the availability of m channels, rendezvous between two start-asynchronous users is guaranteed within a delay of m time slots. The expected time-to-rendezvous is m/3 time slots. Assuming users are start-synchronous, rendezvous is made in at most (m+1)/2 time slots. The expected time-to-rendezvous is m/4 + 1 - 1/4m time slots