The luminescence characteristics of human immunoglobulins (IgG and IgM), their light and heavy chains, their Fc and (Fab)2 fragments and of concanavalin A were studied at room temperature and at 77K. The intrachain disulphide bonds were shown to quench the luminescence of immunoglobulins, the effect being more pronounced at room temperature. The interchain and the intersubunit disulphide bonds affected the luminescence only very slightly. Algebraic addition of the luminescence properties of the fragments did not lead to recovery of the luminescence properties of the IgG molecules. The luminescence characteristics of IgG and IgM, and concanavalin A depend on the native structures of these proteins; it was found that the proteins tended to acquire the intrinsic luminescence of tryptophan on denaturation. The antibodies and the concanavalin A molecule showed pH-dependent luminescence properties.