A procedure is described for the isolation of polyribosomes from crude tissue homogenates of germinated pea seeds using Mg2+ precipitation in the presence of the ribonuclease inhibitor heparin. Collection of the polyribosomal pellet does not require the use of an ultracentrifuge. The method has a potentially wide application for polyribosome and messenger ribonucleoprotein isolation and might also be useful where conventional techniques have failed.