Astrology is a pseudo-science based on the assumption that the well-being of humankind, and its health in particular, is influenced in a constant and predictable fashion by the stars and other stellar bodies. Its origins can probably be traced back to Mesopotamia of the 3rd millennium BC and was particularly popular in Graeco-Roman times and the Medieval Era. Astrology in Western countries has always differed from that in the Far East, and while it largely lost its popularity in the West after the Renaissance, it still remains of considerable significance in countries like China and Tibet. Astrology took on a prominent medical component in the Old Babylonian Era (1900-1600 BC) when diseases were first attributed to stellar bodies and associated gods. In the Neo-Babylonian Era (6th century BC) the zodiac came into being: an imaginary belt across the skies (approximately 16o wide) which included the pathways of the sun, moon and planets, as perceived from earth. The zodiac belt was divided into 12 equal parts (“houses” or signs), 6 above the horizon and 6 below. The signs became associated with specific months, illnesses and body parts – later with a number of other objects like planets, minerals (e.g. stones) and elements of haruspiction (soothsaying, mantic, gyromancy). In this way the stellar objects moving through a zodiac “house” became associated with a multitude of happenings on earth, including illness. The macrocosm of the universe became part of the human microcosm, and by studying the stars, planets, moon, etcetera the healer could learn about the incidence, cause, progress and treatment of disease. He could even predict the sex and physiognomy of unborn children. The art of astrology and calculations involved became very complex. The horoscope introduced by the 3rd century BC (probably with Greek input) produced a measure of standardisation: a person’s position within the zodiac would be determined by the date of birth, or date of onset of an illness or other important incident, on which information was needed. Egyptian astrological influence was limited but as from the 5th century BC onwards, Greek (including Hellenistic) input became prominent. In addition to significant contributions to astronomy, Ptolemy made a major contribution to astrology as “science” in his Tetrabiblos. Rational Greek medicine as represented by the Hippocratic Corpus did not include astrology, and although a number of physicians did make use of astrology, it almost certainly played a minor role in total health care. Astrology based on the Babylonian-Greek model also moved to the East, including India where it became integrated with standard medicine. China, in the Far East, developed a unique, extremely complex variety of astrology, which played a major role in daily life, including medicine. During Medieval times in the West, astrology prospered when the original Greek writings (complemented by Arabic and Hebrew contributions) were translated into Latin. In the field of medicine documents falsely attributed to Hippocrates and Galen came into circulation, boosting astrology; in the young universities of Europe it became taught as a science. It was, however, opposed by the theologians who recognised a mantic element of mysticism, and it lost further support when during the Renaissance, the spuriousness of the writings attributed to the medical icons, Hippocrates and Galen, became evident. Today Western standard medicine contains no astrology, but in countries like China and Tibet it remains intricately interwoven with health care. In common language we have a heritage of words with an astrological origin, like “lunatic” (a person who is mentally ill), “ill-starred”, “saturnine” (from Saturn, the malevolent plant) and “disaster” (from dis, bad, and astra, star).