The problem of wetting is discussed in the framework of the variational approach. Derivation of the general equation describing the wetting of rough chemically homogenous surfaces is presented. The equation considers effects related to the line tension at the perimeter of the drop and at the details of the relief. The equation comprises as particular cases the Cassie and Wenzel equations and the equation proposed recently by Wong and Ho. (C) 2011 Elsevier Inc. All rights reserved.