This presentation is an attempt to participate in the process of ‘medical archaeology’ by exploring one of the submerged areas of Oriental medicine, namely the complex and variegated clinical approach to the diagnosis and treatment of Gu syndrome (gu zheng). A review of the modern research literature shows that this topic has remained virtually unexplored in both China and the West. A close examination of the original texts illuminates the mysterious concept of Gu syndrome as a valid clinical approach that may potentially provide an answer to the many invisible ‘demons’ that plague patients in a modem age, namely systemic funguses, parasites, viruses and other hidden pathogens.