A curved array ultrasound transducer is described which is usable in both sector and curved linear modes. The transducer includes a central portion (40) of elements and lateral portions (44) of elements on either side of the central portion. In the sector mode the central portion of elements is operated to perform phased array scanning. In the curved linear mode both the central and lateral portions of elements are operated to perform curved linear array scanning. The transducer elements of the central portion have a finer pitch than the pitch of the transducer elements of the lateral portions. In the sector mode, the elements of the central portion are operated individually, and in the curved linear mode the transducer elements of the central portion are operated in pairs. In the sector mode, the number of transducer elements of the central portion that participate in the active aperture of the transducer may be varied according to the number of transducer elements in acoustic contact with the patient.