The adhesion of the sea anemonesActinia equinaandMetridium senilewas tested on a variety of surfaces, and the force required to remove the anemones related to the surface area of the pedal disc in contact with the substratum. In common with many other marine organisms, anemones were more strongly attached to rough surfaces and those with high free surface energies. Initial measurements suggested that the strength of anemone adhesion was considerably lower than that of comparable intertidal organisms but this was later shown to be an artefact of technique. An improved technique was employed to reduce the incidence of peel during adhesion measurements on Tufnol plates giving tenacity measurements forA. equinaof 4·6 × 105N m−2. The pedal disc secretions of both species stained strongly for proteins and only faintly for acid mucopolysaccharides, showing that proteins play a major role in anemone adhesion.