Introduction Plant-growth-promoting rhizobacteria (PGPR) colonize the rhizosphere of many plant species and confer beneficial effects, such as increased plant growth and reduced susceptibility to diseases caused by plant pathogenic fungi,bacteria, viruses and nematodes [1] . Some PGPR also elicit physical or chemical changes related to plant defense, a process referred to as ‘induced systemic resistance’ (ISR)[2] . ISR elicited by PGPR has suppressed plant diseases caused by a range of pathogens in both the greenhouse andfield [1,2] . However, fewer reports have been published on PGPR as elicitors of tolerance to abiotic stresses, such as drought, salt and nutrient deficiency or excess. The subject of PGPR-elicited tolerance to heavy metals has been reviewed recently [3,4] , so it is excluded from this discussion. Here, we propose the term ‘induced systemic tolerance’ (IST) for PGPR-induced physical and chemicalchanges in plants that result in enhanced tolerance to a biotic stress, and we review recently published workrelated to this subject. Biotic stress is excluded from IST because conceptually it is part of biological control and induced resistance.