Plants of two wheat species (Triticum aestivum cv. Tanit and T. durum cv. Ben Bachir), differing in their sensitivity to NaCl were cultivated in the presence or absence of 100 mM NaCl for 21 days. Soluble proteins extracted from leaves were analyzed by two-dimensional electrophoresis in order to detect NaCl-induced changes in the polypeptide patterns. In all, 500 spots were detected. Results showed species-dependent differences. The greatest alterations in the polypeptide profiles following salt stress were found in the most sensitive cultivar: among the 12 spots (molecular mass, 15-31 kDa) specifically considered in the acidic region of the gel, 11 declined, even disappeared in the NaCl-sensitive leaf profiles, while in the tolerant species only five spots were affected by the salt treatment and five remained untouched; moreover in the latter, two new polypeptides were shown to be induced by NaCl.