Plus-Colchicine prepared from natural material has considerable acitivity in the tubulin binding assay. Replacement of the acetamido side chain with an oxo group also affords active materia. Studies done so far indicate that not all of the structural features present in colchicine are necessary for binding to tubulin. Conversion of natural colchicine into demecolcine has not yet been accomplished. Isoquinolines prepared from mescaline and containing 6 aromatic methoxy groups are not active in the tubulin binding assay.