The study of the friction occurring at a Hertzian contact (i.e., the contact between a sphere and a flat surface or between two spheres) has always been a central issue in nanotribology, since realistic interfaces may be approximated by numerous individual Hertzian contacts that are within certain boundaries statistically distributed in all three dimensions. However, the theoretical description of the mechanical behavior of such contacts under load considering adhesion has been difficult in the past. Generally applicable models (i.e., models covering the "intermediate regime" between small, hard and large, soft contacts, as they might be most frequent in actual interfaces) required always numerical approaches. In this talk, I will present a new theory that covers the full parameter range for an adhesive Hertzian contact, but results in a simple equation describing the effective load acting on the surface that consists of adhesive and external contributions. The theory is based on a model interaction force that includes both short-range and long-range components. Comparison with numerical results obtained from the Maugis-Dugdale model as well as with experimental friction force microscopy data demonstrates the validity of the new approach.