Ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and RuBPCO binding protein (BP) were isolated from barley leaves. RuBPCO was dissociated into subunits under denaturing conditions. Polyclonal antibodies against RuBPCO, RuBPCOBP and RuBPCO large subunit (LS) were raised. Inununoblotting analyses showed that anti-RuBPCO antibodies did not cross-react with BP. Anti-BP antibodies cross-reacted with RuBPCO smáli subunit (SS) and reacted but more slightly with RuBPCO LS.