Capsaicin, existing in fruit, is the major pungent component of Capsicum spp. Pungency is a hereditary feature but is also influenced by environmental factors and cultural applications. It does not only add flavor and spice to the food but also useful for medical or therapeutic purpose due to pharmacological and physiological effects in human. In addition to its repelling property for pests such as insects and mites, it is used against some pathogenic fungi and bacteria, especially in organic agriculture. However there is limited information on its metabolism, its transport, and its impact on plant growth In this paper, it is given short information about capsaicin which used since ancient time, and results of some investigations dealing with capsaicin are reviewed.