Technical Abstract: White snakeroot and rayless goldenrod cause “trembles” and “milk sickness” in livestock and humans, respectively. The toxin in white snakeroot and rayless goldenrod was identified in 1927 and 1930, respectively as tremetol. It was reported that the toxin in white snakeroot disappears as it is dried, and that completely dried plants were incapable of producing “trembles” or “milk sickness”. Conversely, it has been reported that the rayless goldenrod toxin was not destroyed by drying and that the plant is toxic either fresh or dry. In this study the concentrations of tremetone, dehydrotremetone, and structurally similar compounds were determined in white snakeroot and rayless goldenrod before and after various drying conditions. Tremetone, dehydrotremetone and structurally similar compounds in rayless goldenrod and white snakeroot are most stable upon freeze drying, followed by air drying and least stable upon oven drying (60 °C). Also demonstrated is that tremetone is stable and that dried white snakeroot and rayless goldenrod are capable of inducing toxicosis in livestock.