The termination kinetics of methacrylic acid (MAA) radical polymerization in aqueous solution containing 10 wt % MAA was measured via the single pulse-pulsed laser polymerization-electron paramagnetic resonance (SP-PLP-EPR) method from 0 to 50 degrees C. The termination rate coefficient, k(u) was determined as a function of radical chain length. Addition of high-molecular-mass poly(methacrylic acid), which mimicks monomer conversion, leads to a reduction of k(u), which is however far below the associated decrease in fluidity, eta(-1).