The carbon isotope discrimination(δ~(13))of leaves has been shown to be correlated with the transpiration efficiency ofleaves in a wide range of species.This has led to δ~(13)C being used in breeding programs to seiect for improved transpirationefficiency.The correlation between δ~(13)C and transpiration efficiency was determined under well-watered conditions duringthe vegetative phase in six genotypes of lentil(Lens culinaris Medikus),six genotypes of chickpea(Cicer arietinum L.)and 10cultivars of narrow-leafed lupin(Lupinus angustifolius L.).Biomass(dry matter)accumulation and water use(transpiration)varied among the genotypes in all three species and transpiration efficiency was 40% to 75% higher in the most efficientcompared with the least efficient genotypes.However,δ~(13)C and transpiration efficiency were not significantly correlatedin any of the species.This suggests that the δ~(13)C technique cannot be used in selection for transpiration efficiency in thethree grain legumes(pulses)studied. The carbon isotope discrimination (δ ~ (13)) of leaves has been shown to be correlated with the transpiration efficiency of leaves in a wide range of species. This led to δ ~ (13) C being used in breeding programs to seiect for improved transpirationefficiency.The correlation between δ ~ (13) C and transpiration efficiency was determined under well-watered conditions was the vegetative phase in six genotypes of lentil (Lens culinaris Medikus), six genotypes of chickpea (Cicer arietinum L.) and 10ultivars of narrow- leafmass lupin (dry matter) accumulation and water use (transpiration) varied among the genotypes in all three species and transpiration efficiency was 40% to 75% higher in the most efficientcompared with the least efficient genotypes.However , δ ~ (13) C and transpiration efficiency were not significantly correlated with any of the species. This suggests that the δ ~ (13) C technique can not be used in selection for transpiration efficiency in the three grain legum es (pulses) studied.