Melatonin is a main hormone of pineal gland. Melatonin is produced in periods of darkness and is responsible for changes of circadian rhythms (eg. phases of dream and watches, reproductiveness). Melatonin also acts as antioxidant and antineoplastic agent. Nowadays melatonin can be administered in insomnia, disturbances of twenty-four hours rhythm at blind people, hypertension, irrital bowel syndrom, epilepsy, bronchial asthma. Resently melatonin can be used also in neurodegenerative and cancer disseases.