The dynamics of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) micelle rearrangements were studied using iodine laser temperature jump experiments with light-scattering detection. Two relaxation processes were detected : the first, fast one was accompanied by an increase in scattered light intensity, while the second, slow process was accompanied by a reduction in light intensity. The Aniansson-Wall theory was used to interpret the experimental results. The equilibrium micelle structures at the start and end points of the temperature jump experiment were used as input for the Aniansson-Wall equations. The solution of these equations agrees qualitatively with experimental data and suggests the mechanisms associated with the two time constants. The first time scale, in the tens of microseconds to about 10 ms range, is attributed to unimer insertion into micelles. The other time scale, in the 1-100 ms range, is associated with the rearrangement of the micelle size distribution. It is shown that the second process is often not observed either because the unimer supply is insufficient or because the micelle number density is not temperature dependent.