Analyses were performed on 20 tuff samples from the surface of 13 rock-cut Buddhas in Ohita (Japan) to determine changes in the chemical composition caused by environmental decay. Nineteen elements were identified using neutron activation analysis. Remarkable variations were observed in calcium content, which was particularly high in the surface crust, forming carbonate or sulphate. Aluminium was generally enriched in highly deteriorated portions. Manganese and rare earths may serve as indicators of different origins. Map, table, 1 reference.