Both argon plasma electrosurgical coagulation (APEC) and conventional electrosurgical fulguration (CEF) apply electrosurgical energy to the target tissue through a plasma. Presented here is a detailed examination of this process. Consideration of the fundamental processes and characteristics of plasmas and the various parameters they are dependent upon illuminates and explains the similarities and differences between APEC and CEF. Both APEC and CEF provide non-contact and self-limiting coagulation. The electrical and chemical differences between air and argon are, however, manifested in very different plasmas and tissue effects. Chief among these are the much greater working distance achievable with APEC, its uniformity of tissue effect and the softness of the eschar it produces. The variance of these characteristics and effects as functions of parameters under the control of the surgeon is examined both theoretically and experimentally. Measurements of tissue damage show that they vary with working distance, generator power, and time more controllably and predictably with APEC than with CEF. CEF is shown to have application for pin point coagulation while APEC excels at controlled coagulation of larger areas with greater uniformity of depth.