A 1969 official report on the state of conservation of the frescoes called for their restoration and set guidelines for exploratory investigations designed to ascertain whether any 15th-century painting survived below the 18th-century alterations. A wide range of analytical techniques was used, many of them for the first time in regard to wall paintings in situ. For characterization of the surface topography and the underlying structures, the following noninvasive techniques are discussed: photogrammetry; thermography echography; and double exposure laser holography. For examination of the nature and condition of the original paint and plasters and added materials, stratigraphy, microchemistry, infrared photography, ultraviolet fluorescence, and spectrophotometry were used. Other work carried out concerned environmental studies and cleaning methods. Architectural alterations to the chapel were defined, and further findings helped resolve important art historical issues on the art of early Renaissance Florence. -- AATA