The isotopic composition of rainwater near Nahariya, Israel, was measured in 12 individual storms during the winter months of 1980/1981. Rains most depleted in the heavy stable isotopes and enriched in tritium are associated with air masses which come from North East Europe and have a short, intense interaction with the East Mediterranean Sea. Storms most enriched in 18O and D and depleted in tritium are associated with air masses which come from the Atlantic Ocean and enter the Mediterranean Sea on its western part, travelling along the North African Coast, sometimes with a southerly shift. A relatively high correlation coefficient was found between the stable isotopic content of precipitation and the 800 mb temperature.