To facilitate the selection of samples for 14C dating, shells from coastal deposits were analyzed by light microscopy, X-ray diffraction, scanning electron microscopy, and isotope analysis. One or more of these techniques made it possible to detect contamination by old and young carbon and to identify appropriate pretreatment procedures. Microscopic inspection and X-ray analysis are especially useful when applied to aragonitic mollusks as contamination is often calcitic and thus readily detected. Death assemblages, when correctly selected, provide reliable ages for coastal deposits, but in certain circumstances dates determined on these assemblages were found to be superior to dates for tracing shorelinesTo facilitate the selection of samples for 14C dating, shells from coastal deposits were analyzed by light microscopy, X-ray diffraction, scanning electron microscopy, and isotope analysis. One or more of these techniques made it possible to detect contamination by old and young carbon and to identify appropriate pretreatment procedures. Microscopic inspection and X-ray analysis are especially useful when applied to aragonitic mollusks as contamination is often calcitic and thus readily detected. Death assemblages, when correctly selected, provide reliable ages for coastal deposits, but in certain circumstances dates determined on these assemblages were found to be superior to dates for tracing shorelines.