A field study was conducted in Maryland to estimate nonsummer stomatal conductances on clear days for two invasive woody vine species common to the southeastern United States. Before the first frost in late October stomatal conductances were similar for kudzu (Pueraria lobata) and Japanese honeysuckle (Lonicera japonica). When minimum predawn air temperature fell to ‚àí0.6 ¬8C kudzu leaves were irreversibly damaged whereas maximum daily conductance in honeysuckle was unaffected. Maximum conductances in honeysuckle increased to 14 mm s‚àí1 in late November and mid-December similar to late-spring and summer values. When minimum air temperatures decreased to ‚àí2.8 ¬8C in January conductance still remained above 5 mm s‚àí1. Maximum daily conductance was lowest in early March corresponding with low leaf temperatures. By mid-April maximum conductance increased to 10 mm s‚àí1. Conductances suggested that rates of leaf gas exchange in honeysuckle during fall winter and spring were relatively high. Carbon gain during this period might thus contribute substantially to the invasive growth characteristic of the species.