The influence of tension, pressure, and weight on different aspects of pipe and riser behavior has already been the subject of many articles (see references). In spite of this it has frequently been misunderstood, sometimes with serious consequences. The object of this paper is to explain the subject clearly and the approach is therefore deliberately very elementary. The principal problems of bending, buckling, yielding and strains, usually treated in separated papers, are here treated homogeneously. The widely used concepts of “effective tension” and “effective stress” are given interpretations, easy to visualise, which are related to analogous concepts in other engineering fields. Finally, eight diverse particular examples of the influence of tension, pressure and weight on pipe and riser behavior, are discussed.