One of the important causes of deterioration of several Indian monuments is the corrosion of iron clamps and dowels used for their construction. The increase in volume of iron as a result of corrosion causes cracking, breaking, and bulging of stone slabs. At open joints brown stains of rust are developed. X-ray diffraction, infrared, and metallographic studies were carried out on the dowels/clamps and their corrosion products. In the light of the results obtained the mechanism of corrosion of dowels and clamps has been discussed. Since removal of dowels/clamps is difficult from huge monuments, in situ treatment of iron dowels/clamps is suggested. -- AATA