The article describes the problems encountered by the Science Branch of Archaeological Survey of India in the chemical cleaning of the surface of the Taj Mahal. The marble surface needs to be periodically cleaned of accumulations of dust, smoke, tarry matter, etc. Due to meteorological and topographic conditions, the city is very hot and dry and is very much dust-laden. Their effects are manifested in the appearance of yellowish brownish accretions on the inaccessible portions of the Taj Mahal. Human vandalism also plays a part in the process of deterioration. The article describes the various steps undertaken by the Science Branch, and suggests remedial measures.