The use of herbicides in South Vietnam between 1962 and 1971 was reviewed, including the nature and quantities of herbicides used, their handling and application. Emphasis was placed on Herbicide Orange, a 50:50 mixture of 2, 4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4, 5-T), with its associated contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) . The at-risk US military population in South Vietnam was defined to establish the potential for exposure in handling and application of Herbicide Orange. The environmental fate of the phenoxy herbicides and TCDD was reviewed to evaluate the potential for human risk associated with exposure to areas previously treated with Herbicide Orange. The occupational and environmental aspects of the project to incinerate at sea 2.22 million gallons of Herbicide Orange during the summer of 1977 were summarized to assess the potential for human exposure in handling large quantities of the material. Scientific data were reviewed on incidents and episodes involving suspected poisoning of humans or animals by phenoxy herbicides or TCDD. Literature dealing with animal toxicology and the effects of human exposure to 2,4-D, 2,4,5-T and TCDD was reviewed to correlate exposures with symtomatology.