Brassinosteroids are plant hormones whose functions have been discovered in the past years. In order to confirm scientifically the biological effects caused exclusively by these compounds, different tools can be used, such as BRdeficient or BR-perceptive mutants, molecular studies, biological assays, application of brassinosteroid biosynthesis inhibitors, endogenous quantification and exogenous application. This work aims at relating the physiological effects in plants when exposed to different dosages and analogues of brassinosteroids during different phases of development (germination, flowering, fructification) and when submitted to biotic and abiotic stress (pathogens, water stress, saline stress, hypoxia, temperature, heavy metals and pesticides) as well as the particularities related to tropisms, circadian rhythms and interactions with other plant hormones. The use of brassinosteroids with the objective of increasing crop yield in the field and to improve the quality of the seedlings has also received attention in recent papers. The main objective of this chapter is to discuss the physiological effects that occur in cells, tissue or whole plants when submitted to brassinosteroid applications, taking into account the possible mechanism of action of these compounds and their practical use in agriculture, describing the analogues and the dosages used in field and laboratory experiments during the last 10 years. [ABSTRACT FROM AUTHOR]