Abstract A technique of destabilization of KB cell plasma membrane by treatment with hypotonic citrate buffer was employed. The technique did not alter the viability or ability of the cells to synthesize macromolecules or produce virus, but did permit the visualization, by the freeze-fracture technique, of plasma membrane modifications occurring in response to adenovirus adsorption. The modifications consisted of a rearrangement of the membrane particles (MPs) on both protoplasmic and external leaflets of the plasma membrane. The rearrangement delineated bare areas, 139 nm in mean diameter, devoid of MPs and protruding outwards. The membrane changes were transient and were only observed when KB cells were maintained with adenovirus particles at 0 °C. The changes disappeared rapidly upon warming to 37 °C, reforming the ‘random pattern’ of MPs, normally visible on the cell plasma membrane. The same type of study was carried out with purified adenovirus capsid components (hexon, penton, penton base and fiber), with smaller virus particles (poliovirus) and with larger ‘artificial’ adenovirus particles made of latex beads coated with adenovirus pentons. The dimensions of the bare regions devoid of MPs appeared to be related to the size of the particles used, suggesting the existence of a ‘recognition pattern’ specific for virus particles.