This review aims at comprehensively presenting the state-of-the-art of Ultrasound-Assisted Drying (UAD). UAD represents a promising hybrid drying technique that enhances drying rate and energy efficiency while preserving the quality of the materials being dried. However, in accordance to literature, the limited knowledge and capacity of ultrasonic equipment still prevent this technology from being used in practical industrial applications. The first part briefly described the fundamentals of ultrasound. One major challenge of developing UAD is its multidisciplinary nature; the intention is to extend our knowledge on acoustic science in order to understand the role of ultrasound in drying enhancement. The second part encompasses the latest UAD studies; they are focused on four research subjects: 1) UAD equipment 2) Influence of ultrasound on drying performance 3) Parametric analyses 4) Impacts of ultrasound on the quality of dried materials Progress has been made in the last two decades, but to date, researchers are not fully capable of explaining certain contradictory observations such as those presented herein. This review synthesizes the published results and analyzes them with respect to the specific drying conditions; then, some explanations are suggested. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.