Monoclonal antibodies specific for neurofilament proteins, glial filament protein, or myelin basic protein were used with immunohistochemistry for evaluation of a series of 14 human benign and malignant teratomas for the presence of these neural specific antigens. The results indicate that human teratomas can express all of these neural antigens, reflecting the presence of differentiated neurons, astrocytes, and oligodendroglia, respectively. Although the tumors were selected because neural tissue had been noted on microscopic examination, 2 of the 15 cases lacked all of these neural antigens, and both were malignant teratomas. In the remaining cases, 2 or 3 of these neural antigens were detected. The presence of all 3 was correlated with the presence of mature, and the absence of immature, neural elements. The immunohistochemical detection of these antigens allows the confident recognition of neural elements in human teratomas, and their presence may be of prognostic significance.