The expanding protein sequence and structure databases await methods allowing rapid similarity search. Geometric parameters-dihedral angle between two sequential peptide bond planes (V) and radius of curvature (R) as they appear in pentapeptide fragments in polypeptide chains-are proposed for use in evaluating structural similarity in proteins (VeaR). The parabolic (empirical) function expressing the radius of curvatures dependence on the V-angle in model polypeptides is altered in real proteins in a form characteristic for a particular protein. This can be used as a criterion for judging similarity.