The vesicant agents of the unitary chemical munitions stockpile include various formulations of sulfur mustard [bis-(2-chloroethyl) sulfide; agents H, HD, and HT] and small quantities of the organic arsenical Lewisite [dichloro(2-chlorovinyl) arsine; agent LI. These agents can be dispersed in liquid, aerosol, or vapor form and are capable of producing severe chemical burns upon direct contact with tissue. Moist tissues such as the eyes, respiratory tract, and axillary areas are particularly affected. Available data summarizing acute dose response in humans and laboratory animals are summarized. Vesicant agents are also capable of generating delayed effects such as chronic bronchitis, carcinogenesis, or keratitis/keratopathy of the eye under appropriate conditions of exposure and dose. These effects may not become manifest until years following exposure. Risk analysis derived from carcinogenesis data indicates that sulfur mustard possesses a carcinogenic potency similar to that of benzo[a]pyrene. Because mustard agents are alkylating compounds, they destroy individual cells by reaction with cellular proteins, enzymes, RNA, and DNA. Once begun, tissue reaction is irreversible. Mustard agents are mutagenic; data for cellular and laboratory animal assays are presented. Reproductive effects have not been demonstrated in the offspring of laboratory rats. Acute Lewisite exposure has been implicated in cases of Bowen's disease, an intraepidermal squamous cell carcinoma. Lewisite is not known to generate reproductive or teratogenic effects. This paper is the second in a journal series of review articles synthesizing pertinent toxicological data on chemical wafare agents scheduled for destruction by the Department of the Army (DoA) in the 1990s. The first paper in this series (1) summarized recommended treatment/decontamination protocols for the organophosphate nerve agents VX [S-(diisopropylaminoethyl)methylphosphonothiolate, o-ethyl ester], GA [Tabun; N-N-dimethylphosphoroamidocyanidate, ethyl ester], and GB [Sarin; methylphosphonofluoridate, isopropyl ester] as well as the vesicant (blister) agents H, HD, HT [various forms of sulfur mustard, bis(2-chloroethyl)sulfide], and Lewisite [an organic arsenical, dichloro (2-chlorovinyl)arsine]. The current paper focuses on the acute and delayed toxicity of vesicant agents, some of which are known carcinogens. The Department of Defense Authorization Act of 1986 (PL 99-145) directed and authorized the Secretary of Defense to destroy the United States' stockpile of lethal unitary chemical munitions and agents by September 30, 1994. The Act was amended in 1988 to permit operations