A method of extracting recovering oil from vegetable material in which oil bearing material is heated and subjected to sonication at least one frequency above 400 kHz, removing a first yield of oil by decanting and subjecting the retained material to centrifugal separation to separate out a second yield of oil. Preferably the raw vegetable material is passed through a screw press and the obtained material is heated and subjected to the ultrasonic treatment and then allowed to settle for a predetermined period before decanting the oil layer. Preferably two frequencies above 400 kHz are used, one below 1 MHz and the second from 1 MHz. There are many potential transducers arrangements possible for producing standing waves.