The 2013 MedSeA oceanographic cruise along the Mediterranean Sea was an essential part of the European project "Mediterranean Sea Acidification in a changing climate - MEDSEA" (http://medsea-project.eu/) , within the FP7 Cooperation program. The MedSeA campaign is also part of an international program GEOTRACES that aims to characterize and study the seawater dissolved elements.Potentiometric titration of Alkalinity was measured in a closed cell, according to the DOE handbook of methods for CO2 analysis (DOE, 1994; http://cdiac.ornl.gov/oceans/DOE_94.pdf). The precision of AT analysis was determined to be ± 2 µmol/kg. The accuracy of AT measurements was determined to be ± 1 µmol kg-1 by analyzing Certified Reference Material (Andrew Dickson, CA, USA).Potentiometric titration of Inorganic Carbon was measured in a closed cell, according to the DOE handbook of methods for CO2 analysis (DOE, 1994; http://cdiac.ornl.gov/oceans/DOE_94.pdf). The precision of CT analysis was determined to be ± 4 µmol/kg. The accuracy of CT measurements was determined to be ± 4 µmol/kg by analyzing Certified Reference Material (Andrew Dickson, CA, USA).