Brassinosteroids (BRs) are a group of naturally occurring plant steroidal compounds with wide ranging biological activity. Because BRs control several important agronomic traits such as flowering time, plant architecture, seed yield and stress tolerance, the genetic manipulation of BR biosynthesis, conversion or perception offers a unique possibility of significantly increasing crop yields through both changing plant metabolism and protecting plants from environmental stresses. Genetic manipulation of BR activity has indeed led to increases in crop yield by 20–60%, confirming the value of further research on BRs to improve productivity.