Differentiation of syndromes is a method of understanding and diagnosing disease by the theories of traditional Chinese medicine. The diagnostic procedure involves an analysis of the clinical data regarding symptoms, physical signs, and disease history, together with information obtained from an application of the four diagnostic methods. Only correct differentiation can give a correct diagnosis and thus a suitable method of treatment.

Therefore the four diagnostic methods are the basis of the differentiation of syndromes, and the differentiation of syndromes is the basis of clinical treatment. Furthermore, the effect of clinical treatment is the criteria of judgment for the correctness of the deduced differentiation. These three aspects form an organic connection - a basic law of diagnosis and treatment in traditional Chinese medicine, that is, "applying the treatment on the basis of differentiating syndromes."

There are a variety of methods for differentiating syndromes: differentiation according to the eight principles; according to the theory of zang-fu organs; according to the theory of six channels; accord to the theory of wei, qi, ying, and xue; according to the theory of the sanjiao; according to the theory of qi, blood, and body fluids; according to etiology, etc. Each of these methods has its own characteristics and emphasis, while in clinical practice they are interrelated with each other and complement each other.

Regarding content, the differentiation of syndromes according to the eight principles is the dominant procedure and the differentiation of syndromes according to the theory of zang-fu organs is the basis of all the other methods. Other methods of differentiation can be separated from these two. Therefore this book mainly introduces the method of differentiating syndromes according to the eight principles and the theory of zang-fu organs.