Despite international treaties with strong verification measures that aim to prohibit and prevent the use of weapons of mass destruction, nevertheless some countries and terrorist groups have developed, produced and used such weapons. Successful management of casualties from chemical warfare agents strongly depends on fast and appropriate medical treatment, on the ability of first responders to take proper action, and on new and more effective counter-measures. Although the general principles of clinical toxicology, such as decontamination, stabilization, patient evaluation and symptomatic treatment are similar for many toxicants, chemical warfare agents deserve special attention because their very high toxicity, rapid onset and multiple organ involvement with lethal evolution. This report describes briefly the toxicity and the medical management of mass casualties with chemical warfare agents. Characteristic diagnostic signs and therapeutic schemes for these agents are described. The importance of the knowledge of medical and emergency personnel as well as that of military nuclear, biological or chemical (NBC) unit preparedness and improving research in the field of chemical warfare are emphasized.