Background: An electronic radial array echoendoscope has been developed that uses the same US processor as the linear array instruments made by the same company, thereby eliminating the need for two processors. The performance of this prototype instrument was compared with that of a mechanical radial echoendoscope in patients. Methods: Fourteen patients underwent sequential examinations with both echoendoscopes in random order. Predefined criteria were used to evaluate the performance of each instrument. Results: The quality of the electronic radial image was rated as “good” or “superior” to that of the mechanical radial echoendoscope in 12 patients. In 2 patients, imaging with the prototype was inferior because of positioning and/or operator inexperience. The forward-viewing optics of the prototype enhanced intubation and instrument advancement. Limitations included excessive stiffness of the tip of the instrument that resulted in occasional slippage from the duodenum. The prototype provided an adequate diagnosis in 12 patients and was superior to the mechanical radial endoscope in terms of diagnosis in 2 cases. Conclusion: The prototype electronic radial echoendoscope provides US images of similar quality and is equivalent in terms of clinical utility to the mechanical radial echoendoscope.