<jats:title>Abstract</jats:title><jats:p>A simple and relatively rapid technique is described which can be used to determine accurately the overall pattern of macromolecule biosynthesis in plant cells. <jats:italic>Sanguinaria canadensis L. (Papaveraceae</jats:italic>) suspension cells were used as the model system. The patterns of DNA, RNA and protein synthesis were determined through cellular incorporation of [methyl‐<jats:sup>3</jats:sup>H]‐thymidine, [5‐<jats:sup>3</jats:sup>H]‐uridine and [4,5‐<jats:sup>3</jats:sup>H]‐leucine, respectively. The method takes advantage of a one‐step filtering procedure, which simplifies the extraction methods normally used. The results are described and possible applications of this procedure in plant‐cell growth studies and biotechnology are discussed.