Recent findings of Herpesvirus-type particles in human tissue culture cells originating from “normal” and cancerous individuals have been described. Negative stain studies on the fine structure of these particles (EB-3) indicate that they belong to the herpes group of viruses. However, isolation, immunofluorescence and “coating” tests have ruled out the possibility that this virus is Herpes simplex, Herpes zoster, varicella or cytomegalovirus.It has recently been suggested that members of the papova virus group, although all having the same number of capsomeres, are distinguished from each other by the type of lattice skew present on their capsid. We attempted to detect a similar morphological distinction between the Herpesvirus-type particles and the virus of Herpes simplex. Figure 1 demonstrates the presence of three six-fold capsomeres located along the edge of a triangular face in between two five-fold capsomeres. Since these five capsomeres are located along a straight line the capsid must have a regular icosadeltahedral lattice and must have 162 capsomeres. This makes it identical to the capsid of Herpes simplex virus. We have also repeatedly observed the presence of dark “furrows” on the surface of particles permeated with phosphotungstic acid (PTA) (Fig. 2). Their disposition is compatible only with a regular icosahedral lattice.