A new method, utilizing image analysis on TLC, was developed for the determination of zygacine, the neurotoxic steroidal alkaloid in death camas (Zigadenus venenosus). The quantitative detection level of zygacine on TLC was 1 µg. Diurnal changes in zygacine levels were not evident, nor were there differences in zygacine levels in death camas growing at high- or low-elevation habitats. The image analysis method was also applied to the determination of vanillylveracevine in Zigadenus elegans.