An experiment was carried out to test whether or not it is possible to date rock art assemblages relatively by measuring the reflectance of repatination. Visual examination of repatination in rock art has long been used to order elements chronologically, with the assumption being made that continued accumulation of patina results in a darker color. This study uses a densitometer/reflectometer to provide quantitative values for the relative darkness, or reflectance, of the repatination within art elements and on immediately adjacent unworked panels. Sixty-nine petroglyph elements were measured from the Coso Range in California. Two types of elements were included: atlatls, previously identified as dating to ca. 1,000-200 BC; and bowmen, dating to AD 300-1000. Although a significant difference in relative chronology between the two element types was expected, no major differences in reflectance could be measured. Problems that complicate the use of reflectance measurement of repatination for relative dating of rock art are discussed. These include the fact that even within a small area there can be considerable variation in the color of the rock used for the petroglyphs; petroglyph elements are sometimes pecked only part way through the original patinated surface; and the degree of darkening is not always age-dependent, but also depends upon the chemical composition of the patina. See also <i>AATA</i> <b>Vol. 22, Abstract No. 99,</b> PARIS No. 70105. -- AATA