Mice were vaccinated three times at 4 week intervals. Two weeks after the last vaccination mice were challenged with ricin. P values compare survival of ID vs. IM vaccinated mice within a dose level; ∇ = 10 μg, △ = 1.0 μg, ○ = 0.1 μg, X = 0.01 μg, □ = 0 μg; challenge via (A) IP injection, at the 0.1 μg dose level, P = 0.078, (B) gastric gavage, at the 0.01 μg dose level, P = 0.218, (C) aerosol, at the 0.1 μg dose level, P = 0.848. (A) and (B) represents 2 experiments of 8 mice each combined into groups of 16 mice for analysis; (C) represents 4 experiments of 4 animals each combined into groups of 16 mice for analysis.