Herbicide 2,4-D formulated as a urea-type “polymer” was readily destroyed by long-wave uv (356-nm) irradiation, whereas conventional 2,4-D was more resistant. The opposite relationship was noted for “polymeric” and conventional formulations of dicamba. “Polymerized” 2,4-D was more resistant to thermal degradation (60°C) than “non-polymerized” formulations. Ultraviolet degradation of “polymerized” 2,4-D was eliminated by the incorporation of RYLEX-H and UVINUL D-50, industrial uv absorbers. Exposure of “polymeric” dicamba to 60°C heat, followed by trapping of the volatile component, indicated that 21 percent was lost by thermal degradation and 46.6 percent by volatilization. Comparable values for “non-polymerized” dicamba were 37.9 and 60.1 percent.