A kinetic modeling study is presented for batch nitroxide mediated polymerization (NMP) of methyl methacrylate (MMA; nitroxide: N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)] (SG1)). Arrhenius parameters for SG1 disproportionation (A=1.4 10(7) L mol(-1) s(-1); E-a=23 kJ mol(-1)) are reported, based on homopolymerization data accounting for unavoidable temperature variations with increasing time, that is, nonisothermicity. For low targeted chain lengths (TCLs300), this nonisothermicity is also relevant for NMP of MMA with a small amount of styrene. Parameter tuning to copolymerization data confirms a penultimate monomer unit effect for activation (s(a2)=k(a12)/k(a22)=6.7; 363 K; 1: MMA; 2: styrene). To obtain, for a broad TCL range (up to 800), a dispersity well below 1.3 an initial styrene mass fraction of ca. 10% is required. An interpretation of the comonomer incorporation is performed by calculating the fractions of activation-growth-deactivation cycles with a given amount of monomer units and the copolymer composition distribution. (c) 2018 American Institute of Chemical Engineers AIChE J, 64: 2545-2559, 2018