An extension of the methods employed in the isolation of (trans) 1H/2H-decafluorocyclohexane,1 (I) from the polyfluorocyclohexane mixture obtained by the vapour phase fluorination of benzene with cobalticfluoride at about 150°, has afforded the four remaining members of the series of decafluorocyclohexanes [the cis- and trans-1H:3H- and 1H:4H-isomers (1H:3H/-(IV), 1H/3H-(III), 1H:4H/-(VII), and 1H/4H-(VIII)