Pioneering studies in the late 1800's and early 1900's already demonstrated the induction of resistance to infectious agents in plants by abiotic stress and microorganisms. Starting in the 1990's, this topic generated increasingly strong interest for its potential in crop protection and it developed into a very dynamic field of research which produced more than 20000 scientific publications in the last 20 years. A working group of the International Organisation for Biological Control (www.iobc-wprs.org) has been fully dedicated to scientific exchanges on this topic since 1998. Over the years, commercial preparations with plant defense-inducing properties have been developed and they are increasingly registered as plant protection products in many parts of the world for use both in organic and conventional agriculture. Plant defense inducers rarely provide 100% protection against pests or infectious agents, and the consistency of their efficacy may be a challenge in field conditions. However, plant defense inducers present unique advantages that make them particularly useful tools for Integrated Pest Management. These features will be presented and remaining challenges for their practical inclusion in integrated protection schemes will be evoked, highlighting needs for future research.