Highly specific monoclonal antibodies (McAbs), 1aM3, 2aM1 and 2bM2 were produced and characterized against Sh. flexneri 1a, 2a and 2b respectively. IaM3 is an IgG3 (lambda) type antibody reactive against whole bacteria or the lipopolysaccharide (LPS) only; 2aM1 is an IgG1 (kappa) type antibody which reacts with the polysaccharide component of LPS; 2bM2 is an IgG3 (lambda) type antibody which binds with both the polysaccharide and protein/peptide components of the LPS. The results indicate that specific McAbs with diagnostic potential can be produced using acetone-killed and dried cells as antigen. Ascitic fluid produced in mice using the anti-Sh. flexneri hybridomas was found not to contain higher titres of McAbs against the bacteria. A "nutritionally-deprived" medium was, therefore, constructed which produced greater than five times the concentration of the McAbs than that could be obtained using normal culture fluid.