Actin microfilaments in isolated root-tip cells from wheat (Triticum aestivum L. cv. Kite) were visualized by immunofluorescence microscopy using two different antiactin monoclonal antibodies. Cells in interphase contain predominantly subcortical bundles of microfilaments, as described in many cell types, but in preprophase and prophase cells, immunodetectable actin is organized solely in ordered arrays of cortical microfilaments that cover the entire surface of the cell, transverse on lateral faces, random on end walls. Intermediate stages with random and transverse microfilaments are also seen on lateral faces. The cell cycle stage-dependent transverse cortical microfilaments described here are previously unreported in higher plant cells.