The distribution of tubulin in brain tissue has been investigated by light and electron microscopic immunohistochemistry using an antiserum raised against electrophoretically purified microtubule derived tubulin. The specificity of the staining is indicated by the lack of staining when non-immune serum is substituted for anti-tubulin serum and the quite different staining obtained with antisera against antigens other than tubulin. The anti-tubulin immunohistochemistry reveals tubulin antigen in microtubules and in the postsynaptic junctional lattice of most synapses. No antigen has been detected in either the synaptic cleft or in the axon terminal. This distribution confirms previous biochemical identification of tubulin as a major postsynaptic junctional component, but suggests that it is not common to all synaptic junctions.