Fasad i.e. venesection is an old classical method of treatment in the Unani system of medicine. Fasad is Arabic word which means “to open”. In the process, complete evacuation which drains out blood and dominating humours mixed with blood from veins. Fasad is carried out when the kamiyat (quantity) of the blood is excess in the body and patient is either exposed to the risk of developing a disease or has actually developed one. In classical literature of Unani system of medicine, physicians wrote a lot about this procedure. The details of venesection is mentioned in the given paper on the basis of classical literature including history, indications, types, amount of blood to be venesected, time, person, procedure, complications and special focus has been made on the number of vessels to be venesected and their benefits with respected to disease and condition.