3 April 2018This article investigates conditions under which high prices, in conjunction with low levels of pollution, signal environmentally clean products. It is shown that, when consumers cannot ascertain the environmental performance of products, the price must be distorted upward to signal a clean product. A clean producer saves less from emitting pollution and so raises price and restricts output with less reluctance than does a dirty producer. The theoretical result of over-pricing is consistent with the evidence that “green” products receive higher prices than conventional products. However, optimistic prior beliefs of high-environmental performance may cause signaling to fail.