Twenty human meningiomas were examined for IgG and IgM by the direct 
immunofluorescence of immunoperoxidase methods, or both. IgG was conspicuously 
found in and around the blood vessels, whorls, and psammoma bodies. It was also 
clearly present on the cytoplasmic membranes of the tumour cells. On the other 
hand, IgM was seen only within the blood vessels. Significance of these findings 
is briefly discussed including possible humoral immune reactions in regard to 
whorl and psammoma body formation in meningioma.