ABSTRACT. – Recent mortality events of Pinna nobilis registered in the western Mediterranean coasts highlight the need to monitor regularly populations of this endangered endemic bivalve. The present study has investigated a total surface of 6,400 m2 of 4 protected areas from France and Monaco registering density of individuals and biometric data of each population. Herein, densities of 3.56 individuals·100 m–2 in the Embiez archipelago, 6.81 individuals·100 m–2 in the Natural Reserve of Scandola, 1.37 individuals·100 m–2 in the National Park of Port-Cros and 5.25 individuals·100 m–2 in the Underwater Reserve of Larvotto. These values, with great number of adults and juvenile individuals, support the healthy and consolidated status of these populations.