Technical Abstract: Larkspur (Delphinium spp.) poisons thousands of cattle on western rangelands each year. As poisoning does not cause specific lesions and poisoned animals are rarely found before they die, definitively identifying poisoned animals is difficult. Additionally, toxin concentrations in larkspur plants vary with environment, plant, and location. Rapid, sensitive and specific diagnostic techniques are needed to identify poisoned animals and to determine when and what plants are likely to poison livestock. In this study, three competitive inhibition enzyme-linked immunosorbent assays (CI-ELISA) for toxic larkspur alkaloids were developed. One assay is class specific toward the N- (methylsuccinimido)anthranoyllycoctonine (MSAL) alkaloids, while two assays are specific for individual alkaloids. The assay with the lowest limit of detection had an I50 of 191 pg with a limit of detection of 30.5 pg for methyllycaconitine. Spike and recovery studies using bovine blood and brain tissue ranged from 52-89%. These findings suggest that with additional development these techniques are likely to be excellent tools to diagnose poisoned animals and identify highly toxic plants.