In this study, a novel ultrasonic vacuum (USV) drying technique was used to shorten the drying time of fish fillets. For this purpose, ultrasonic treatment and vacuum-drying were simultaneously performed to dehydrate salmon and trout fillets at 55 degrees C, 65 degrees C, and 75 degrees C. In addition, the USV technique was compared with vacuum-drying and oven-drying techniques. The dehydration kinetics of the fillets was successfully described by seven thin-layer drying models with R-2 range between 0.944 and 1.000. Depending on drying temperatures and fish species, the drying times could be shortened using the USV technique between 7.4% and 27.4% compared with vacuum-drying. The highest effective moisture diffusivity was determined in the fillets dried with the USV technique and they increased with increasing drying temperatures. Ultrasonic treatment accelerated the vacuum drying process for the fillets; therefore, this technique could be used to improve the efficiency of vacuum-drying for the fillets. (C) 2015 Elsevier B.V. All rights reserved.