We present the results of an experimental investigation of the temporal evolution of plasmas produced by high power laser irradiation of various types of target materials. We obtained 'high-quality' interferometric data on the evolution of the plasma electronic profile, which can be directly compared with analytical models and numerical simulations. For aluminium and plastic targets, the agreement with 1D simulations performed with the hydrocode MULTI is excellent, at least for large times (t ⩾ 400 ps). In this case, simulations also show that the effect of radiation transport is negligible. The situation is quite different for gold targets for which, in order to get a fair enough agreement, we must take radiation transport into account.