The purpose of this study was to measure some aspects of the water relations of selected plant species in the alpine tundra, Colarado, in order to assess the possible role of water limitation on primary production. Leaf water potentials were measured in Kobresia myosuroides, Geum rossii, Bistorta bistortoides, Deschampsia caespitosa, and Caltha leptosepela. Leaf resistances to water loss were measured in Bistorta and Caltha. Measurements were made at dawn and midday throughout the season and several times through selected days in plants along a moisture gradient. Leaf resistance was related to leaf water potential, light, and temperature. Leaf water potentials decreased throughout the season and were higher on the wetter site. Minimum water potentials of the species in the order listed above were —40, —23, —17, —31, and —17 bars. Minimum leaf resistances of Bistorta and Caltha were 0.8 and 1.6 s.cm—1, respectively, and were lower on the wetter site. Both Bistorta and Caltha on the wet meadow showed partial midday stomatal closure, but Bistorta on the dry meadow did not At —16 bars leaf resistance increased abruptly in Caltha, but was still low in Bistorta. Leaf resistances were low at incident solar radiation levels of 0.2 ly ° min—1and at temperatures near 20°C. Leaf resistances increased with temperatures below 15°C. Root resistances for Bistorta were 0.9 x 104s ° cm—1° bar—1at the dry site and 0.8 x 104at the wet site, and for Caltha were 0.6 x 104s ° cm—1° bar—1at the wet site. The changing daily pattern of leaf water potential and leaf resistance is shown to be related to the diurnal environmental pattern, to root resistances, and to the relationships between leaf resistance and leaf water potential and between leaf water potential and leaf relative saturation deficit.