Propagation rate coefficients (k(p)) for the homopolymerization of methyl acrylate (MA) and dodecyl acrylate (DA) were determined by the pulsed laser polymerization (PLP)/size-exclusion chromatography (SEC) technique at pressures between 100 and 2000 bar. The activation volumes for the propagation step, Delta V-#(k(p)), of MA and DA are identical within experimental accuracy, but are clearly different from the previously reported Delta V-#(k(p)) of methyl and dodecyl methacrylate. For both the alkyl acrylates and methacrylates a pronounced family-type behaviour of k(p) is seen, with k(p) being slightly enhanced toward larger ester size.