The pattern of localization of actin filaments was compared in whole mounts of lens epithelium of rabbit and mouse using the fluorescently-labeled actin-specific probe, rhodamine-phalloidin. In the adult rabbit lens, fluorescent polygonal arrays consisting of central vertices and interconnecting filaments were present in the apical end of each epithelial cell. Electron microscopy confirmed that these arrays lined the cytoplasmic side of the apical membrane. In the mature adult mouse, polygonal arrays were not seen either with fluorescence or electron microscopy. Instead, the actin was packaged in a single, elongated, often curved bundle near the epithelial cell apex, referred to as a "sequestered actin bundle" or SAB. The SAB often appeared attached to the plasma membrane and to approach the perinuclear basket of microfilaments. The significance of the differences in these two patterns of actin is discussed in terms of differences in the accommodative ability and static lens shape in these two animals.