This paper describes an annular CMUT ring array designed and fabricated for the tip of a catheter used for forward-looking intravascular imaging. A 64-etement, 2-mm average diameter array is fabricated as an experimental prototype. A single element in the array is connected to a single-channel custom front-end integrated circuit for pulse-echo operation. In conventional operation the transducer operated at around 10 MHz. In the collapsed regime, the operating frequency shifted to 25 MHz and the received echo amplitude tripled. The SNR is measured as 23 dB in a 50-MHz measurement bandwidth for an echo signal from a plane reflector at 1.5 mm. We also performed a nonlinear dynamic transient finite element analysis for the described transducer, and found these results are in good agreement with the experimental measurements, both for conventional and collapsed operation. © 2004 IEEE.