Ultrasonic imaging techniques play an important role in endoscopic pre-operative staging and post operative follow-up of tumour patients as well as for the assessment of cardiac insufficiency. However, cancerous lesions offer only low-contrast targets. Therefore, high sensitivity systems with good contrast as well as flexible and robust handling are required to obtain diagnostic accuracy and confidence. We developed a radial scanning ultrasonic catheter with a total diameter of 2.3 mm, which makes use of a LIGA geared micromotor to turn an ultrasonic transducer directly at the tip of the catheter. Connector rings fitted on a shaft as well as sliding contacts transmit the 20/30 MHz signals from the transmitter/receiver of an ultrasound monitor system (Kretz Technik AG, Austria) to/from the rotating transducer. Due to its excellent performance and easy handling the scanner module will be applied in a number of ultrasonic diagnostic applications.