Water uptake and transport were studied in eight liana species in a seasonally dry tropical forest on Barro Colorado Island Panama. Stable hydrogen isotope compo- sition (SD) of xylem and soil water soil volumetric water content (Bv)and basal sap flow were measured during the 1997 and 1998 dry seasons. Sap flow of several neighbor- ing trees was measured to assess differences between lianas and trees in magnitudes and patterns of daily sap flow. Little seasonal change in 8 was observed at 90-120 cm depth in both years. Mean soil water SD during the dry season was -19%0 at 0-30 cm -34%0 at 30-60 cm and - 5 W i at 90-120 cm. Average values of xylem SD among the liana species ranged from -28% to 4 % 0 during the middle of thedryseasonsuggestingthatwateruptakewasrestricted to intermediate soil layers (30-60 cm). By the end of the dry season all species exhibited more negative xylem SD values (-4lYm to -62%0) suggesting that they shifted to deeper water sources. Maximum sap flux density in co- occurring lianas and trees were comparable at similar stem diameter (DBH). Furthermore lianas and trees conformed to the same linear relationship between daily sap flow and DBH. Our observations that lianas tap shallow sources of soil water at the beginning of the dry season and that sap flow is similar in lianas and trees of equivalent stem diame- ter do not support the common assumptions that lianas rely