The aim of this research was to investigate glycinebetaine (Glybet) accumulation in rice seedlings via the activity of betaine aldehyde dehydrogenase (BADH) and to characterize the physiological responses of Glybet-accumulated seedlings to salt stress. The BADH activity of Thai jasmine rice seedlings cultured photoautotrophically showed a progressive elevation during the first four days after growth under salt-stress condition (342 mM NaCl), but gradually decreased thereafter (days 6-8). This increase in BADH activity was accompanied by an accumulation of Glybet. In contrast, the BADH activity and Glybet content of control seedlings (0 mM NaCl) remained at a low and constant level during the same 8-day interval. Significant reductions in the concentrations of chlorophyll a, chlorophyll b, total chlorophyll and total carotenoid of salt-stressed seedling were observed with increasing exposure time to salt-stressed conditions. The decrease in total chlorophyll concentrations of salt-stressed seedlings was positively related to reductions in the net photosynthetic rate (r = 0.89), and dry weight (r = 0.89). The dry weight of in-vitro salt-stressed seedling was positively related to their survival percentage (r = 0.94). The survival percentage of salt-stressed seedlings was significantly decreased with increasing exposure time to the salt-stressed conditions. The Glybet accumulation in salt-stressed rice seedlings is consistent with a defense response to salt-stressed conditions. These results suggest that assaying BADH activity and/or Glybet accumulation may be further used in screening for salt-tolerant varieties of indica rice.