Using pulse lasers for initiation in conjunction with online spectroscopic detection of monomer conversion and with size exclusion chromatographic analysis of polymer molecular weight distribution has enormously improved the knowledge about free-radical polymerizations up to high pressure. The novel procedures which partly include modeling of the full molecular weight distribution are outlined. The survey primarily addresses propagation and termination rate coefficients of homopolymerizations up to 3 kbar with special emphasis on the conversion dependence of termination rate. In addition, recent results on reactivity ratios in ethene-acrylic ester copolymerizations and on initiator decomposition rates are presented.