Perfusion-fixed tissue blocks were incubated in high molar sucrose solutions, shock frozen in melting isopentane, and sectioned on a conventional cryostat. Semithin sections (2-4 microns) alternatingly stained for parvalbumin and glutamate decarboxylase enabled us to demonstrate the coexistence of both antigens in the same cell. Thick sections (40 microns) of central and peripheral nervous system tissue were immunostained and processed for correlated light and electron microscopic studies. At the electron microscopic level, the preservation of ultrastructural features such as membranes and synaptic contacts was comparable to that normally seen in vibratome sectioned material. Hence, this technique can successfully be used for preembedding coexistence studies and electron microscopic preembedding immunocytochemistry when vibratome sectioning is problematic.