Analysis of the adhesive contact between solids makes use of contact mechanics, surface physics, and fracture mechanics. The elastic adhesive contacts have been intensively studied, and now, interest still remains about how the viscoelasticity of the solids may be taken into account for the calculation of the work of adhesion, the major difficulty being to separate the surface and bulk energy dissipations. This paper describes a new and original experimental device for "dynamic JKR" tests, which allows us to study dynamic adhesive contacts under a cyclic normal load. PDMS contacts on PDMS were studied at different frequencies and temperatures, and it was possible using the JKR model to determine the hysteretic value of the work of adhesion. The results obtained follow the same evolution as the loss factor of the material.