Hormones play an important role in insect behaviour. These hormones are mainly the neurohormones of the brain and of the corpus cardiacum, the juvenile hormone of the corpus allatum and the ecdysone of the prothoracic glands. These produce either releaser effects or modifier effects. Hormonal modulation of neurophysiological activity controlling various aspects of behaviour, hormonal influence of reproductive behaviour in the male and the female insects, their role in migration, as well as hormonal influence of caste determination and behaviour of social insects, have been discussed.