The termination behavior in the stationary free radical copolymerization system styrene (ST)-methyl methacrylate (MMA) at 25 degreesC was reexamined by means of two newly developed methods. In essence, these are adaptations of the now already familiar methods of determining k(t) from rates and degrees of polymerization, originally developed for analysis of pulsed laser polymerization (PLP) experiments, for steady-state experiments conducted by photoinitiation using a continuous light source. Like the earlier methods they allow for the determination of the termination coefficient k(t) as a function of chain length. The extent of the chain length dependence of k(t), characterized by the parameter b in the power law connecting k(t) and radical chain length v', k(t) = A(v')(-b) is found to be on the order of 0.1 over the full composition range (including the two monomers ST and MMA) which is slightly smaller than the data obtained from PLP for the two pure monomers (0.16-0.18). However, there are no large variations as a function of feed composition. The absolute values of kt either obtained via extrapolation to unity chain lengths (k(t)(1,1)) or calculated for a fixed chain length of 500 (k(t)(500)), however, pass through a maximum. In view of the diffusion-controlled character of the termination reaction this result is interpreted by assuming the mobility of the chain ends to be increased when a monomer unit different from the terminal unit is incorporated into the penultimate (or penpenultimate) position of the growing chain, especially if MMA is replaced by ST in a MMA terminated chain. Assisted by the alternation tendency of the copolymer system ST-MMA this might finally lead to an overall chain end mobility in excess of that of either homopolymeric radical for intermediate monomer compositions.