An ultrasonic endoscopic probe is provided with an articulating distal tip (14) at which an ultrasonic transducer (130) is located. The articulating section (30) of the probe can be locked in an articulated position by a lock control (28,28') located at a control section (10) of the probe. The locking force is variably selectable by the user, so that the articulating section (30) will be locked in position by a desired force. The articulating section (30) is controlled by cables (74,76,129), which include cable tension adjustments (70a,70b) that also serve to delimit the range of articulation. The articulating section (30) is formed of alternating pivot rings (120) with intervening polymeric pivot beads (106), which provide repetitively smooth articulation. The ultrasonic transducer (130) is rotatable to steer the acoustic scan plane during use, and a sliding membrane (164) between the transducer (130) and its acoustic window (162) allows the transducer (130) to rotate smoothly without sticking.