Immunology as an independent discipline is just I 00 years old. In the Pasteurian era, it was the direct handmaiden of medical microbiology, but with Landsteiner's discovery of the blood groups in I 90 I , immunology burst through into other fields. This spreading of immunology into many facets of biology and medicine has con tinued at an accelerating pace, particularly over these last 20 years. For the physician, immunology is a 'horizontal' specialty, breaking the confines of a single organ system and touching an enormous number of chronie diseases. This spreading tendency of immunology is both a source of great fascination and great frustration. The research worker in immunology is delighted to be engaged at so many frontiers. The clinician who must use the new research knowledge to help the patient can easily be confused and overwhelmed. The fact that immunology is poorly taught in most medical courses makes things worse. These are the reasons why physicians, clinical pathologists and undergraduate and postgraudate students should hail the publication of 'Diagnostic Immunology and Serology'.