The Authors have investigated the possible interaction between narciclasine and DNA using various physico-chemical techniques useful for demonstrating the complex formation between a small molecule and a marcomolecule. The data obtained clearly indicate that a complex between DNA and narciclasine does not occur. The mechanism of the antimitotic activity of narciclasine must therefore be of a different nature, such as interference with the enzymatic systems involved in the duplication of DNA or with the protein structures involved in nuclear division.