This chapter aims to review the current status of induced disease resistance signalling research. It mainly focuses on the roles of salicylic acid (SA) and jasmonic acid (JA) in the signalling cascades involved in the different types of induced resistance. The chapter covers two important topics in induced resistance research namely pathway crosstalk and priming. The role of JAs and ethylene (ET) in the regulation of plant growth promoting rhizobacteria (PGPR) ‐ and plant growth promoting fungi (PGPF) ‐ triggered systemic defence responses has been mainly established through the analysis of JA ‐ and ET ‐ signalling mutants. However, colonization of the roots by induced systemic resistance (ISR) ‐ inducing PGPR is often not associated with an increase in the production of these hormones. Hormonal crosstalk is thought to equip the plant with a powerful regulatory capacity to finely tune its immune response to the attacker that is encountered.