When the drug design target is a receptor for which there is no experimentally determined three dimensional structures, it is often useful to construct models of the receptor site. These models may take the form of graphical surfaces, grid points surrounding the legends, or model atoms and functional groups. A receptor surface model is a hypothetical model that characterizes the putative active site of a receptor. It is based on the construction of surfaces to represent spatial & electrostatic properties of receptor active site. A receptor surface model is visually intuitive and modifiable as the hypothesis is refind. It allows computations comparable to those that can be performed with traditional atomistic models.