Chapter 1 of this book provides a fascinating, historical account of the use of cannabis across many cultures and centuries. Suffice it to say here that any natural substance with over 5000 years of medical history will have attached to it a heritage of hearsay and legend through which one must sift to identify areas of true therapeutic potential for us in the late twentieth century and beyond. A summary of conditions for which cannabis has been used, ranging through various shades of rationality, appears in Table 1.