In this paper a general analysis on contour line determination of surfaces of revolution, as well as an algorithm for its computation and computer aided representation has been performed. A contour line of a surface of revolution (being a plane curve, when surface of revolution represented in certain projection) is being obtained as a projection of a space curve lying on the surface, which divides its visible from its invisible part. It has been shown that the space curve can be obtained as arr intersection of the surface and its view-dependent polar cylinder which is generated by a particular family of spheres. The surface, being the envelope for the family of spheres, with each sphere has a parallel i.e. a circle of revolution in common. Thus, the space curve can be determined in the analytical form so that it can be treated by means of differential geometry. Once the curve and its projection that is the contour- line of the surface are determined, a base for creation of a simple visibility criterion is got avoiding in that way any later hidden line removal.