This paper presents the experimental results of using ultrasonic waves to mitigate the fouling of the hollow-fiber ultrafiltration (UF) membrane process. While sonication has been reported to effectively enhance the performance of flat-sheet membrane filtration systems, little information is available regarding hollow-fiber membrane even though hollow-fiber has been a popular membrane configuration for industrial applications. In this work, both online continuous and offline pulse ultrasonic irradiation processes have been employed and their effectiveness on the fouling mitigation were evaluated and reported. The effects of ultrasonic frequencies and power intensities on the permeate flux were evaluated employing a synthetic clay solution. Experimental results indicated that sonication at higher intensity and lower frequency substantially reduced membrane fouling and in turn enhanced the permeate flux of the filtration process. Published by Elsevier B.V.