C23H25NO7.1⁄2C4HsO2, M r = 471.49, is o r t h o r h o m bic, P212121, with a = 9.299 (3), b = 10.534 (4), c = 27.084 (6) A, V = 2653 (4) A 3, z = 4, 2(Mo Ka) = 0.71069 A, D c = 1.180, D m -1.16 (2) Mg m -3. The structure was solved by the Patterson search approach where the molecular structure of isocolchicine was used as the search model and refined by full-matrix leastsquares methods. The final R value was 0.077 for 1552 observed reflections. The ethyl acetate molecule shows an occupation factor of 0.5, and the acetamido O atom is disordered. The position of the acetoxy group in the solid state defines the molecule as belonging to the isocolchicine series. The conformation of colchiceine acetate may explain its lack of accessibility at the tubulin binding site and therefore its decreased biological activity.