Cytomegalovirus (CMV) has been shown through pathologic examination to infect many cell types of the brain; however, neuropathology specific for CMV has been difficult to prove in the absence of classic cytomegalic cells or demonstration of CMV antigens. In an effort to further understand CMV infection of brain tissue, a human brain cell aggregate system was infected with several strains of CMV. Different neuropathologic changes were observed that were related to CMV strain and multiplicity of infection. These changes were consistent with those considered characteristic for human immunodeficiency virus (HIV) infection, including a nodular and multinucleated giant cell formation. By electron microscopy, only a few cells throughout the aggregates demonstrated intranuclear virions. These cells were identified by ultrastructural morphology as either monocyte derived macrophages or microglial cells (M/M). Antigen expression was observed in these cells with and without neuropathologic changes. Infection progressed in either a diffuse fulminant manner or a more focal cell to cell spread. These studies demonstrate that CMV selectively infects M/M in normal human brain cultures and suggests differences in neuropathology based on multiplicity of infection and strain variation.