The aim was to explore the effects of delmopinol, a substituted amino-alcohol compound recently reported as a potential antiplaque agent, on GTF activity in solution and when adsorbed on to sHA. Delmopinol was without a significant effect on GTF activity in solution. In contrast, a reduction in the bound glucans synthesized by the adsorbed GTF was found in the presence of delmopinol. Delmopinol did not displace the adsorbed GTF from the sHA, nor was there significant desorption of glucans from sHA. The total glucan synthesis (bound and unbound) was reduced in the presence of delmopinol. Inhibition of GTF was not reversed by sucrose. Inhibition of GTF activity by delmopinol apparently results from drug-enzyme interaction on the surface of sHA beads. These observations provide further support for the important differences in the properties of adsorbed GTF and GTF in solution, illustrating that GTF-drug interaction differs between enzyme adsorbed to surfaces and enzyme in solution.