A new concept for controlled radical polymerization in the presence of stable free radicals is presented. Due to irreversible side reactions of free polymer radicals, the amount of dead polymer chains and, consequently, the concentration of stable free radicals increases during the polymerization reaction (Figure 1). Therefore, only monomers with the ability to constantly thermally initiate radical polymerization (e.g., styrene) to capture the excess counter radicals are susceptible to this type of polymerization. In contrast, we present a self-regulating process in controlled radical polymerization, which allows controlled radical polymerization of monomers with no spontaneous initiation. The increase of stable free radicals in our approach is prevented by slow decomposition of the counter radicals and by simultaneous formation of new initiating species. To prove this concept, two triazolinyl radicals (4 and 7) with different thermal stabilities have been studied. Their difference in stability shows a remarkable effect on their use as additives for the controlled radical bulk polymerization of styrene and MMA. The procession of the polymerization in the presence of spirotriazolinyl 7, a stable radical, again strongly depends on the initiating properties of the monomer. While the polymerization of styrene is very well controlled, polymerization of MMA in the presence of spirotriazolinyl 7 could only be accomplished to very low conversions. In contrast, triazolinyl 4, a less stable radical, is additionally able to effectively control the polymerization of MMA at comparably low temperatures.