Cultivation of rice plants (Koshihikari, IR4595 and IR28) in 250 mmol/L NaCl over 16 days provided interesting profiles of responses on a flow-through electrochemiluminescence (ECL) system with tris(2,2'-bipyridine)ruthenium complex. Although some time lags were noted among these rice plants, the increment in the ECL responses was clearly observed on the 11th day. The obtained ECL response profiles were consistent with the proline profiles obtained by HPLC. Such consistency demonstrated that the present ECL system would find a utility as a useful sensor for salt stress on rice plants.