(18)O/(16)O ratios from the juices of a number of fruits and vegetables were measured and found to be isotopically more enriched than the water in which they grew. Fast-growing high-water-content vegetables exhibited less enrichment than slower growing fruits such as apples, pears, and plums. (18)O/(16)O measurements were also made on the water from various sections of several plants, and the enrichment was found to occur in the following order: leaves > fruit > stem >/= ground water.D/H and (18)O/(16)O measurements were made on a series of grape juice samples and, when plotted against each other, gave a slope of 3.9, indicating that the physical process causing this enrichment was probably evaporation, i.e. evapotranspiration.