Five-sevenths of the globe are covered by the sea. In the oldest civilizations the sea was mainly used for navigation and fishing purposes, and then for transportation and commerce. Later, since the sixteenth century the sea was used for the purposes of discovery and conquest of new lands beyond the horizon. Boundary disputes have been present for centuries. The focal point of this work is the question related to the maritime boundary between Ecuador and Peru taking into consideration the official position, the relationship between the rules of international law, state practice and jurisprudence, the evaluation of the considerations for settling the maritime boundary between Ecuador and Peru, and the proposal of actions for the solution of the disagreement. As the first step for delimitation purposes the ICJ has shown a clear tendency to apply the principle of equidistance for delimitation purposes, and then special circumstances (like the presence of islands) have often been taken into consideration in order to achieve an equitable solution. Among special circumstances islands have always played a special role.