A novel in-vitro test system was designed for measuring the duration of adhesion of discs containing various putative mucoadhesive materials to a mucosal surface on application of a constant tensile stress. Rat small intestine was used as the model mucosal surface and all experiments were completed in pH 6.0 isotonic phosphate buffer at 37°C. In all cases adhesive joint failure resulted from a cohesive failure within the hydrating dosage form. As expected, increasing the force applied to the mucoadhesive joint resulted in shortening of the duration of adhesion. A rank order of duration of adhesion for various mucoadhesive materials was obtained, which differed markedly from the rank order of adhesive strength reported in the literature. The neutral polymer hydroxypropylmethyl cellulose, reported to have moderate mucoadhesive properties, showed the longest duration of adhesion when subjected to a constant stress of 0.0846 N. Generally, the greater the reported rate of swelling, the shorter the duration of adhesion. It is suggested that a mucoadhesive dosage form capable of rapidly forming strong interactions with the mucosal surface, but only allowing limited hydration to form a rigid gel, would be the ideal candidate for stable long term mucoadhesion.