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. Immunoblotting analyses showed that anti-RuBPCO antibodies did not cross-react with BP. Anti-BP antibodies cross-reacted with RuBPCO small subunit (SS) and reacted but more slightly with RuBPCO LS.