Human being has always been suffering from diseases. Before the beginning of Ṭibb (medicine) (300Bc), superstitions were considered as the cause of disease. Therefore, Gods and Goddesses were worshipped to cure disease and regain health. Since the existence of medicine, the material is considered a cause of disease. Accordingly, treatment shifted towards the material. In 500 BC Buqrat (Hippocrates) started the discussion of health. He established the views of structure, composition, properties and functions, health and disease in respect of the human body. So, the goal of Greek medicine is to protect health to the possible extent and cure disease. Hippocrates proposed the concept of AkhlāṭArbaa (four humours/four fluid) these are Khilṭ-i- Dam (sanguineous humour), Khilṭ-i-Balgham (phlegmatic humour), Khilṭ-i-Ṣafrā (choleric humour) and Khilṭ-i-Sawdāʼ (melancholic humour). He also proposed that the harmonious state of four humours is responsible for health. And, disharmony results in disease. Every humour is attributed to specific qualities, characteristics and some specific and general functions. But the main function of these Akhlāṭ (humours) is to provide nutrition and replenishment of every organ of the body according to their temperament. Choleric humour is synonymously called yellow bile or bilious humour. Yellow bile is one of the four humours, responsible for health and disease. In abnormal state yellow bile can produce a number of diseases called bilious diseases. In U.S.M. (Unani System of Medicine) bilious diseases are discussed under the heading of Sū-i-MizājMāddῑ (morbid temperament associated with substance). In this paper, a brief explanation of yellow bile along with it relates is given. Pathophysiology of bilious diseases is given in detail.