The rate of photochemical degradation of aqueous solutions of picloram under ultraviolet light was measured by five different methods of analysis. These were chosen to assay the loss of picloram, dechlorination, alteration or loss of the aromatic amino group, loss of aromaticity, and decarboxylation. The initial rate and mean rate of reaction were determined in each case, and their relationship to each other was used to assess the significance of that particular reaction to the overall degradation of picloram and its early degradation products. Results suggest that dechlorination is the major photochemical process, with decarboxylation, loss of aromaticity, and deamination all being significant subsequent reactions.