The present work suggests a theory of reverse combustion linking (RCL). RCL is a central unit operation of underground coal gasification (UCG) technology. The theory is based on analyzing the stability of different branches of the propagation speed curves and determining the regime that is responsible for propagation of the flame during RCL. The theory is in good qualitative and quantitative agreement with the data obtained in practical use of RCL in UCG operations. (c) 2007 The Combustion Institute. Published by Elsevier Inc. All rights reserved.