Astrology as applied to medicine has very ancient roots, for example in India, China and Egypt, but it reached its fullest flowering in Europe in the late medieval and early modern periods, c1450-1700. The influence of astrology also entered European medicine from the Arab countries. Basically it is no exaggeration to say that astrology dominated everything during that period and thus many systems of knowledge depended upon it, were symbiotic with it, or made reference to it in their worldview. In the case of medicine, astrologers assigned signs of the zodiac to rule over parts of the body, planets to rule over organs and systems, and planets to rule over diseases and drugs. Thus the whole system is one of observation and interpretation based upon a complex system of given Rulerships.
Briefly the organs of the body are ruled as follows:
| S.No | Human Parts | Planets |
| 1 | Brain and Nerves | Mercury [and Uranus] |
| 2 | Respiratory | Mercury |
| 3 | Heart | Sun |
| 4 | Arteries | Mars |
| 5 | Veins | Saturn |
| 6 | Kidneys | Venus |
| 7 | Liver | Jupiter |
| 8 | Digestive system | Venus |
| 9 | Muscles | Mars |
| 10 | Reproduction | Venus and Mars |
| 11 | Endocrine system | Neptune and Uranus |
| 12 | Testes | Pluto |
| 13 | Ovaries | Moon |
| 14 | Skin | Saturn |
| 15 | Teeth Nails and Hair | Mars |
| 16 | Bones and Skeleton | Saturn |
By analyzing the planets, its position, aspect, Charam and power with their ruling time the diseases to be ascertained.
