This investigation was designed to clarify the potential role of basic antigens in immune complex nephritis. The GBM is negatively charged and binds cationic substances. We studied 1) whether chemically cationised proteins can bind to the GBM, act as planted antigen, and induce 'in situ' immune complex formation or 2) if a pre-formed cationic antigen antibody complex can localise in the GBM. Results obtained with 5 chemically cationised proteins support the first possibility.