Reelin, the extracellular matrix protein defective in reeler mutant mice, plays a key role during brain development. We therefore raised antibodies directed against various reelin epitopes in order to facilitate biochemical and cell biological studies of this important molecule. Homozygous reeler mice with a large deletion of most of the reelin gene were immunized with fusion proteins and carrier-coupled peptides corresponding to parts of the reelin sequence. Monoclonal antibodies were produced using classical procedures, screened using ELISA and-or western blot prepared with the antigen, and tested by immunohistochemistry and immunoprecipitation assays to detect endogenous reelin. The labeling of Cajal-Retzius cells in the embryonic mouse telencephalon was selected as criterion for positivity in immunohistochemistry. A total of 11 monoclonal antibodies were obtained, providing useful additions to the widely used antibody CR-50. Five are directed against the N-terminal part of reelin, among which three recognize the region that has significant similarity with F-spondin, and two are specific for hinge region located downstream from the F-spondin similarity region and upstream from the reelin repeats. Six antibodies are directed against the C-terminal part of reelin, among which one anti-peptide antibody recognizes the highly basic C-terminal segment. Antibodies against the N-terminal region stain well in immunohistochemistry. By comparison, the labeling of embryonic Cajal-Retzius cells with antibodies directed against the C-terminal region is weaker, suggesting that this part of the molecule might be modified or not be as readily accessible in the tissue as the N-terminus.