Lead white has been the most widely used white pigment in the art of painting. However, when some artists attempted to utilize the pigment in mural painting, great problems occurred due to its transformation into a brownish-colored substance (lead dioxide PbO₂). Research has been carried out in an attempt to explain the process of this transformation, its cause, the nature of the products, and possible methods of reconverting the alteration products to their original color. Salient points of this investigation are summarized here. Remaining unsolved questions are pointed out as well as those that have been clarified. The successful procedure for reconversion of the brown altered pigment is also described.