The salt sensitivity of cucumbers was investigated in two experiments. The electrical conductivity (EC) of the irrigation water used in the experiments ranged from 0.1 to 4.5 mmho/cm at 25°C. In another experiment the specific sensitivity of cucumbers to various salts was studied. There was a linear decrease in the yields of cucumbers as the salt concentration of the irrigation water increased. The yield reduction was about 17% for a 1 mmho/cm increase in the EC. Cucumbers showed a specific sensitivity to excess calcium and magnesium, but most detrimental was the application of sodium bicarbonate. Crop analysis showed that when sodium and chloride were added to the irrigation water, chloride was taken up in much greater quantities by the cucumbers than sodium. The addition of certain ions to the irrigation water not only had an effect on the uptake of the particular ion, but also had a significant effect on the uptake of other ions. The greatest changes in the mineral composition of the leaf occurred as a result of the application of sodium bicarbonate to the irrigation water.