A series of stilbenes, based on combretastatin A-4, were synthesised. A structure-activity study was carried out to characterise the interaction of these agents with tubulin. The substitution of small alkyl substituents for the 4'-methoxy group of combretastatin A-4 and the loss of the 3'-hydroxyl group does not have a major effect on the interaction with tubulin. trans-Stilbenes were shown to bind tubulin, but do not inhibit microtubule assembly. This work, together with previous studies, has been used to propose an idealised structure for a tubulin-binding agent of this type.