The cast bronze doors of the cathedral in Augsburg, dating from the 11th century, have to be restored. Antlerite, acid free paraffin from the last restoration, and various organic acids (probably from earlier treatments) cover the surface. The authors describe the chemical and physical analyses of the 35 bronze plates that are fixed on the two wood doors. They describe the results of the analyses done in 1983-1984 on the conservation done in 1975 with acid free paraffin to determine if the paraffin was in any way related to the corrosion. For the protection of the doors it is proposed to clean the doors mechanically and with organic solvents, and to protect them against weathering with a second door.