The combustion reaction taking place under the typical operating conditions of lean premixed combustors was studied by means of the bifurcation theory. The combustion zone was modeled as perfectly mixed and without coupling with acoustic. Theoretical stability maps were built as a function of the most important operating parameters (heat transfer coefficient, equivalence ratio, and residence time). Self-sustained oscillations were found to occur near blowout at lean conditions in which reaction rate is strongly sensitive to both temperature and fuel concentration. The nature of the arising dynamic regimes is related to thermal effects and, in particular, to the coupling between heat produced by reaction and heat losses.