We photosynthetically characterized two rice cultivars - salt-sensitive‘Annapurna’, and salt-tolerant‘Dongjin’- growing under NaCl stress. Both cultivars showed an increase in $F_{o}$/ $F_{m}$ (the ratio of initial to maximal chlorophyll fluorescence) and a decrease in $F_{v/}$ $F_{m}$ (an indicator of the photochemical efficiency of PS II). In particular, the $F_{v}$ value for Annapurna significant declined while $F_{o}$/ $F_{m}$ was enhanced when plants were exposed to salt stress for 4 d. Annapurna also exhibited more rapid decreases in the coefficients for photochemical quenching (qQ) and non-photochemical quenching (qNP) than did Dongjin. In contrast, zeaxanthin formation was largely influenced by exposure to light rather than to high salinity, with Annapurna having a higher rate of production compared with Dongjin. When both cultivars were exposed to salt stress for 2 d, Annapurna had a much lower rate of photosynthetic oxygen evolution, corresponding to only 46% of the control; the rate for Dongjin was 90% of the control. Salt stress in both cultivars induced the accumulation of two osmoprotectants, glycinebetaine and proline, the rate being higher for the latter. These results indicate that Annapurna is more sensitive than Dongjin to salt stress, in terms of its deterioration in photosynthetic function.ion.n.ion.ion.