Propagation kinetics of butyl acrylate (BA) free-radical homopolymerization in fluid CO2 has been studied by the PLP-SEC (pulsed laser polymerization-size-exclusion chromatography) method at pressures between 200 and 2000 bar and temperatures between -9 and 20 degrees C. The CO2 content was close to 45 wt % in all experiments. As a consequence of the poor chain-transfer activity in solution of CO2, the molecular-weight distributions of the polymer samples show well-resolved PLP structures with at least two, but in most cases three, distinct inflection points. At the p and T conditions of this work, the observed propagation rate coefficients (k(p)) of BA in fluid carbon dioxide at CO2 contents around 45 wt % are found to be about 40% below the corresponding bulk polymerization values. The activation volume and activation energy oft, are, however, identical for bulk and solution (in CO2) free-radical BA polymerizations within experimental accuracy. The origin of the solvent influence on the propagation reaction is discussed. The observed lower values of k(p) in solution of CO2 are assigned to the poor solvent quality of carbon dioxide, presumably resulting in a local monomer concentration at the site of the propagating radical which is smaller than the overall monomer concentration in the system.