Interaction and adsorption of different polyelectrolytes onto mica was studied using the surface force technique. For highly charged polyelectrolytes in dilute aqueous salt solution, the adsorbed layer neutralizes the mica surface charge at a bulk concentration of 10-50 ppm. Upon dilution the adsorbed layers desorb slowly. When the indifferent salt concentration of the solution is increased at a constant polyelectrolyte concentration, additional adsorption takes place. Attractive interactions are present between two layers of adsorbed polyelectrolytes with a charge density of 30% or more as long as the substrate surface charge is not overcompensated strongly. This attraction, which is mainly due to bridging, is considerably stronger than the van der Waals interaction. For uncharged polyelectrolyte/surface systems, the thickness of the polyelectrolyte equilibrium layer increases with decreasing charge density. For the fully charged polyelectrolyte, the range of bridging and steric interaction indicates that the polyelectrolytes adsorb in a flat conformation on the mica surface. Desorption of the polyelectrolytes into a dilute aqueous salt solution is a slow process. For an initially slightly overcompensated system, the long-range and adhesive forces vary with time in contact with a polyelectrolyte-free solution. Initially, the adhesion force increases as the net surface charge decreases. This is due to an increased bridging attraction.