Zooecdysteroids (arthropod steroid hormones) regulate the development of arthropods and probably many other invertebrates. Phytoecdysteroids are analogues occurring in a wide range of plant species, where they contribute to the deterrence of phytophagous invertebrates. The purpose of this short review is to summarise findings on the occurrence, metabolism and pharmacological effects of ecdysteroids in mammalian systems and to draw attention to their potential applications, particularly in gene-switch technology, where ecdysteroid analogues (steroidal and non-steroidal) can be used as effective and potent elicitors.