Prior to the virtual atomic explosion of medical knowledge, at a time when communica­ tion was very much slower, a medical book, to be authoritative and believable, had to be written by a very knowledgable, and, per force, usually quite senior person. The choice of texts was limited and tended to be dominated by a few "classic" (a phrase not quite synonymous with dogma). Following the information explosion, the scenario is quite different. Not only is there a geometric progression in the quantity and speed of devel­ opment of new medical knowledge, but also this development is occurring at very dif­ ferent rates in different countries.