The rate constant for gas-phase reactions of OH radicals with 1H-heptafluorocyclopentene (cyc-CF2CF2CF2CF=CH-) was measured using a relative rate method at 298 K: (5.20 +/- 0.09) X 10(-14) cm(3) molecule(-1) s(-1). The quoted uncertainty includes two standard deviations from the least-squares regression, the systematic error from the GC analysis, and the uncertainties of the rate constants of the reference compounds. The OH-radical-initiated oxidation of cyc-CF2CF2CF2CF=CH- gives the main products COF2, CO, and CO2, leading to negligible environmental impact. For consumptions of cyc-CF2CF2CF2CF=CH- of less than 54%, the yield of the formation of ([COF2] + [CO] + [CO2])/5 (based on the conservation of carbon) was 0.99 +/- 0.02, which is very close to 100%. A possible degradation mechanism was proposed. The radiative efficiency (RE) of cyc-CF2CF2CF2CF=CH measured at room temperature was 0.215 W m(-2) ppb(-1). The atmospheric lifetime of cyc-CF2CF2CF2CF=CH was calculated as 0.61 year, and the photochemical ozone creation potential (POCP) was negligible. The 20-, 100-, and 500-year time horizon global warming potentials (GWPs) were estimated as 153, 42, and 12, respectively.