The effect of supplying high producing Israeli Holstein cows with desalinated or salty water on milk composition and production was examined in the Arava desert of southern Israel. Daily water consumption of cows offered desalinated water was higher by 10.6 L than that of the group offered salty drinking water; DMI was similar for the two groups. Daily production of milk and 3.5% FCM was higher for the cows receiving desalinated water than for the cows receiving salty water; 35.2 versus 33.1 kg and 31.6 versus 29.8 kg, respectively. The percentage of protein in milk and the daily protein production were higher for the cows receiving desalinated water than for the cows receiving salty water: 2.89% and 1.01 kg versus 2.84% and .93 kg, respectively. The percentage of milk fat and the daily fat production were higher for the cows receiving desalinated water. These results indicate that water salinity negatively affects milk production. Improvement of water quality by desalination increased production of milk and milk constituents.