Abstract: Sieving apparatus comprising a sieve carrier, means for imparting longitudinal vibratory movement to the sieve carrier said movement having substantially no vertical component, a sieving medium, a sieve frame to which said sieving medium is secured and supporting said sieving medium at an inclination of not more than 5.degree. to the horizontal, resilient means interposed between the sieve frame and the sieve carrier to support said sieve frame in said sieve carrier, an ultrasonic generator mounted on said sieve carrier and separate from said means for imparting vibratory motion, and coupling means coupling the output from said ultrasonic generator to said sieve frame, in a direction substantially parallel to the plane of the sieving medium.