The analysis of 4 years (1978-1981) of precipitation chemistry data collected by the MAP3S program shows that coastal sites have high concentrations of Cl- and Na+ and a ratio Cl-/Na+ that approximates the seawater value with no significant ''excess'' of any of these ions. At inland stations the concentrations are lower, and the ratio Cl-/Na+ is higher than the seawater value with an ''excess'' of Cl-, which is statistically significant. No significant trend among the inland stations was observed for the Cl- and Na+ concentrations or their ratio.