This is a timely guide on diagnostic methods which will be especially useful to pediatricians, medical students and laboratory technicians who do not have ready access to large medical libraries. Physicians generally know too little regarding the methods employed in providing the data upon which their daily work is based. In the main this lack of familiarity with the principles underlying special tests and procedures can be attributed to the difficulty of obtaining simple explanatory outlines of the methods which are referred to in the briefest manner possible in current journals and textbooks.