An estimate of the surface entergy of polymeric solids can be obtained by wetting measurements. An alternative, in the case of rubber, is to deduce the apparent surface energy by direct optical observations of solid-solid contact areas. This study reports contact observations for the adhesion of rubber hemispheres against glass and plastic substrates. The measurements suggest that the level of adhesion is sensitive to ambient humidity, substrate surface history and viscoelastic reponse of the rubber. Particular emphasis is placed upon the differenc betwenn the making and the breaking of contact. Analysis of the measurements indicates the important roles of surface energy and rubber hysteresis, an increase in either or both leading to higher apparent peel energies but lower adhering energies.