The aim of ťhis study was to clarify whether there are generál differences between the woody and herbaceous plants in their responses to a single non-lethal freezing stress, when measured under comparable conditions. Activity of net photosynthesis (^N33)» th® curves of versus photosynthetic photon fluence density and versus intercellular partial pressure of CO2, and ratio of variable to maximal fluorescence (F^Fm) were measured at optimal temperatures in the leaves of six woody and six herbaceous plant species prior to frost-hardening, after frost-hardening at low positive temperatures and after a single over-night freezing stress (-10 ®C, 12 h) of the shoots. Recovery of at 20/15 “C was also followed. There were no generál differences between woody and herbaceous plants in their photosynthetic responses to freezing stress. In most plants, Pn33 was strongly reduced after freezing mainly due to the disturbances in fimctioning of the chloroplasts, but it recovered within a few days. However, of some herbaceous plants (Cochlearia, one cultivar of spinách) was insensitive to non-lethal freezing. Furthermore, stomatal opening of a few herbaceous plants (Cochlearia, Valerianella) was disturbed after freezing without any sign of an impairment in fimctioning of the chloroplasts.