Proceeding from the hypothesis that cellular differentiation processes are correlated with structural changes of the cell membrane, the expression of antigen and lectin receptors, as well as lectin-like molecules during migration and differentiation of pre- and perinatal neurons in the cerebral cortex, was analysed. It could be shown that a number of cell surface structures exist throughout the whole pre- and perinatal period, e.g. receptors for Robinia pseudoacacia lectin (RPL), pokeweed lectin (PWL) and concanavalin A (ConA) and the Ia and H-2-D/K antigens of the major histocompatibility complex (MHC). The expression of other cell surface structures, for example receptors for peanut and Limulus polyphemus lectin (LPL) and of Thy-1, is determined by the developmental stage; i.e. in the perinatal period higher amounts are found than in early prenatal stages. Binding sites for Phaseolus vulgaris lectin, PWL and anti-Thy-1.2 are not only demonstrated on perikaryal membranes, but additionally on diverse tangential or radial fibre structures. While on cells of the ventricular layer - the proliferating cell compartment - peanut lectin (PNL) receptors are observed in low density, LPL receptors in high density, in the migration zone, i.e. the intermediate layer, receptors are found predominantly for PNL and only few cells carry a significant number of LPL-binding sites. After the preneurons have migrated through the intermediate layer and the neighbouring cortical plate, remaining at the pia-near border of the latter, LPL receptors are again expressed on the cell surface of the now bipolar preneurons, while PNL receptors cannot be demonstrated any more. Experimental evidence is put forward indicating the possibility that this modulation of exposed carbohydrate residues on the cell surface might be mediated by a membrane-associated enzyme system on the same single molecule. For the investigation of neuronal cell interaction the ability of disintegrated suspended preneurons was used to reaggregate spontaneously in vitro and to build histiotypic cell formations within these reaggregates. It was found that this reaggregation of suspended neuronal single cells is dependent on the presence of ionized calcium, on the temperature, and on the conditions that influence the frequency of cell contacts. Furthermore, the structures expressed on the cell surface of preneurons during the pre- and perinatal period were investigated in regard to their influence on the reaggregation of these cells by means of a blockade by monoclonal antibodies or saccharides, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)