The cyclopentadienyl radical decomposition has been studied in detail by high-level correlation MO methods combined with multichannel RRKM rate constant calculations. The product channels of the reaction were examined by calculating their pressure-dependent branching rate constants. The overall reaction rate has been shown to be controlled by the first transition state corresponding to 1,2-hydrogen atom migration. Also, the reverse bimolecular reactions (C 3 H 3 + C 2 H 2 → products) have been included in the study. We provide a summary of pressure dependent rate constant expressions for the 1000-3000 K temperature range that may be useful for kinetic modeling of relevant combustion systems.