The morphology of the Julian Alps and Prealps and of the Triestian Karst are here shortly described; the structures, which defined its origin and development, are also considered. We can notice some cliffs which follow one another from the State boundary to the Adriatic sea; they are made up by lithologic successions, which repeat themselves according to the latitude. Anyway we recognize a general outcropping of rock masses which are decreasing little by little southward as regards the altitude, the age and than the erodibility. There are some differences between the western (Carnian) and the eastern (Julian) bend of the regional mounts according not only to the latitude but to the longitude, because of the lithology. In fact, the Julian mountains often look like the Dolomities in the northern zone. The southern ones, particularly near the high alluvial plain, are rounded and gently dipping. The drainage networks are quite different too. In the upper zone it is a trellis net, in the lower one is locally a trellis net and than it becomes a dendritic system. The glacial erosion follows the same principle too, coming southward along the main and the subordined valley cuts. At last, the Karst morphology shows itself strongly conditioned by the structural scheme as well as by the lateral lithologic changes. It comes out an anisotropic whole of surface forms and of subsurface ones, clearly referred to those reasons. The whole area here described shows moreover a high evolutive dynamics, connected with the recent tectonic phases.