Abstract: The Alecrineiros Shaft is a cave developed in the St. Antonio Plateau, Portugal. This cave develops on a gently dipping monocline structure, along two major fracture families. These discontinuities are sub-vertical and exhibit the following directions: E-W to N70W and N-S to N30E. The shaft presents evidences of several speleogenetic processes compatible with a genesis and development in a vadose regime at the base of the epikarstic zone.