The Committee previously reviewed a draft Health Assessment Document on May 9-20, 1984 and an Addendum is desirable because of newly available data, primarily an inhalation bioassay of rodents by the National Toxicology Program. The Subcommittee believes it is reasonable to describe the weight of the epidemiological evidence in humans as conforming to the EPA guideline for carcinogen risk assessment definition of inadequate. The Subcommittee concluded that the animal evidence of carcinogenicity is limited because of positive results in only one strain of mouse of a type of tumor that is common and difficult to interpret. Therefore, the Subcommittee concluded that perchloroethylene belongs in the overall weight-of-the-evidence category C (possible human carcinogen).