The possibility of using the shells of various fresh water mollusks as indicators of lead levels has been investigated. Shells ofCorbicula manillensis(Asiatic clam) were found to be reliable and readily available indicators of lead levels. Samples collected at a relatively clean site were found to yield a mean lead concentration of 0.6 ppm with a range of .1 ‐ 1.3 ppm. The sample means from other sites were increased by factors between 2 and 3. Also, the shells from very young (less than one year old)C.manillensiscontained unusually high concentrations of lead.