Abstract
Electron microscopy of poliovirus particles and empty capsids under various conditions of specimen deposition and staining visualizes the dissociation products of these particles. The dissociation proceeds in steps; it begins with the expansion of particles and leads to the final product of the dissociation a cluster of several sub-particles of equal size (approx. 100 Å in diam.). A scheme of the dissociation is proposed on the basis of the observed intermediates.