A large part of cytostatics, among them paclitaxel (Taxol.RTM.) and other recently discovered substances that mimic its antitumour effects, have cellular microtubules as their target. The present invention is a high-efficiency homogeneous test based on the use of stabilised microtubules and fluorescent taxoids for detecting any substances that can substitute paclitaxel in its binding site in microtubules, and constituting potentially anticancerous agents.