Since the publication of NTP's draft report (NTP, 1998) on their 2-year inhalation bioassay of ethylene glycol butyl ether (EGBE; 2-butoxyethanol), there has been continued discussion among scientists from government, industry, and academia concerning the human carcinogenic potential of EGBE. NTP (1998; 2000) reported that their study results indicate no evidence of carcinogenic activity in male F344/N rats, equivocal evidence of carcinogenic activity in female F344/N rats based on increased combined incidence of benign and malignant pheochromocytomas, some evidence of carcinogenic activity in male B6C3F1 mice based on increased incidence of hemangiosarcomas of the liver, and some evidence of carcinogenic activity in female B6C3F1 mice based on increased incidence of forestomach squamous cell papillomas or carcinomas. The U.S. Environmental Protection Agency (EPA) IRIS (Integrated Risk Information System) assessment (U.S. EPA, 1999a) concluded that, in accordance with the proposed Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1996), the human carcinogenicity of EGBE cannot be determined at this time, but suggestive evidence exists from rodent studies.