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Using environmental isotopes, the subaquifers of the Judea Group carbonate aquifer were studied from the recharge area in the Judean Hills, eastwards down the flanks of the escarpment to the Jordan River Valley The oxygen isotope data confirm that the dominant source of recharge for the phreatic and confined subaquifers is in the Judean Hills. Water-rock interactions develop the deltaC-13 values rapidly in the recharge region. Once established there is no significant subsequent modification due to interaction with the enveloping carbonate as the waters travel down dip. The relatively high tritium values encountered in the springs and several of the well waters would indicate modern waters. However, that low radiocarbon levels are often encountered in the same water sources implies that a mixture of young water with significantly older water has been encountered. There are indications, at least in the upper subaquifer, of agewise stratification of the waters. Water is transmitted very rapidly through the upper portions of the aquifer while the waters in the lower portions may be moving slowly because of low permeability. The timing of there charge of the deeper portions of the upper subaquifer and much of the lower subaquifer occurred in the mid-to early Holocene.