The joint variation of monthly mean sea level, rainfall, and evaporation recorded in Naples and in other western Mediterranean stations is analyzed. The mass balance among sea level, rainfall, and evaporation and the application of the Wiener filter methods show that the major portion of sea level variance concentrated at annual and semiannual components is dominated by evaporation; the effect of rainfall is less than the effect of evaporation; the Atlantic water flux acts as a balancing source of sea level fluctuations among those of rainfall and evaporation.