this study was undertaken to evaluate the effect of salt stress associated to exogenous spermidine (spd) application on the accumulation of glycine betaine in the pigeonpea genotypes iac fava larga and caqui. the use of this compatible osmolyte as a biochemical-physiological indicator of salinity was also evaluated. the experiment was carried out at unesp, faculdade de ciências agrárias e veterinárias, in jaboticabal (sp), from october to november 2005, in a grow room with irradiance of 190 μmol m-2 s-1, photoperiod of 12 hours, temperature set to 25 oc and the rh to 40%. seeds were sowed in sterile sand with adequate water supply. after 10 days, seedlings were transferred to nutritive solution during 20 days for acclimation. the experiment was then arranged in randomized block design in a 2 x 2 x 4 factorial, corresponding to the genotypes (iac fava larga and caqui), spd rates (control and 0.5 mm) and salt stress (0, 20, 60 and 80 mm nacl). the levels of glycine betaine were determined after 20 days under stress. our results show that glycine betaine can be used as a biochemical-physiological marker of salt stress in the 'iac fava larga'.