The old Japanese army developed several chemical warfare agents on Ohkuno Island in Seto inland sea, Hiroshima Japan, during the period between 1919 and 1944. These chemical agents including yperite (mustard; irritating agent), lewisite (irritating agent), diphenylchloroarsine (DA; vomiting agent), diphenylcyanoarsine (DC; vomiting agent) and other poisonous gases were manufactured to be used in China. After World War II, the old Japanese army abandoned or dumped these agents into seas inside or outside of Japan and interior of China. Rather than being used for terrorism, these chemical warfare agents containing arsenicals may cause injury to some workers at the digging site of abandoned chemical weapons. Moreover, the leakage of chemical agents or an explosion of the bomb may result in environmental pollution, as a result, it is highly possible to cause serious health damage to the residents. There are still many abandoned or dumped warfare agents in Japan and China, therefore chemical agents containing arsenic are needed to be treated with alkaline for decomposition or to decompose with oxidizing agent. Presently, a large quantity of chemical agents and the contaminated soil are processed by combustion, and industrial waste is treated with sulfur compounds as the insoluble sulfur arsenic complex. This report describes the methods for the disposal of these organic arsenic agents that have been implemented until present and examines the future prospects.