Networks of 10 nm filaments were detected in suspension cells ofDaucus carota var.sativa DC, root tip cells ofPisum sativum, mesophyll cells ofBrassica pekinensis and pollen ofNicotiana tabacum by selective extraction combined with whole mount and embedment-free section using diethylene glycol distearate plastic for electron microscopy. Western blot analysis showed that the major filament components are 3 polypeptides of 64kDa, 58kDa, 52kDa, which react strongly with AE3, a monoclonal antibody that recognizes relatively basic keratin — the type II intermediate filaments (IFs) of animal cells -, and 1 polypeptide of 50kDa, which reacts strongly with AE 1, a monoclonal antibody that recognizes relatively acidic keratin — the type I IFs of animal cells. The 10nm plant filaments could be reassembled in a cell-free system. The assembled filaments are indistinguishable from native plant intermediate filament in morphology and protein composition. Thus we demonstrated that keratin intermediate filaments exist in the cytoplasm of higher plants. We also found no obvious tissue or species specificity in the plant IF proteins.