X-Ray analysis of hunterburnine β-methiodide, a quaternary alkaloid isolated from Hunteria eburnea Pichon, has defined the constitution and stereochemistry as (II) and revealed hunterburnine as the first example of a new class of indole alkaloid. Crystals of the methiodide are orthorhombic, space group P212121, with four molecules of C 20H27IN2O2 in a unit cell of dimensions a=10.96, b=18.83, c=9.20 Å. The crystal structure mas solved by the heavy-atom method and the atomic co-ordinates were refined by Fourier and least-squares calculations. The final value of R over 1622 independent reflexions was 15.4%.