The intramembrane specializations at vestibular hair cell-primary afferent synapses have been identified and characterized in complementary freeze-fracture replicas from prehatch and hatchling chick cristae and maculae. Hair cell protoplasmic (P) faces at sites where presynaptic bodies are present exhibit small, tightly packed arrays of 9 nm particles. Hair cell external (E) faces have corresponding arrays of pits. Multiple arrays are often observed in contiguity. Opposite the presynaptic bodies, postsynaptic afferent boutons and calyces exhibit a more extensive array of scattered, irregular E-face particles. Corresponding P-fracture faces of afferent boutons and calyces display little topographical specialization opposite these E-face arrays, which are presumed to be the intramembrane correlate of the postsynaptic density. Examination of complementary replicas has allowed identification of the intramembrane synaptic specializations for all membrane faces at the synaptic apposition.