NN-Bistrifluoromethylethynylamine, (CF₃)₂N·C⋮CH, has been prepared in high yield by the reaction of N-bromobistrifluoromethylamine with acetylene, followed by dehydrobromination of the resultant 1 : 1-adduct, 2-bromo-NN-bistrifluoromethylvinylamine. The bromination of bistrifluoromethylvinylamine to give 1,2-dibromo-NN-bistrifluoromethylethylamine and the dehydrobromination of this adduct, by way of the olefin 1-bromo-NN-bis trifluoromethylvinylamine, also gives the acetylene. N-Bromobistrifluoromethylamine reacts with NN-bistrifluoromethylethynylamine to give 1,2-di(bistrifluoromethylamino)-1-bromoethylene, (CF₃)₂N·CBr:CH·N(CF₃)₂, and this on dehydrobromination gives perfluoro-1,2-bisdimethylaminoacetylene in good yield. The thermal reaction of trifluoroiodomethane with NN-bistrifluoromethylethynylamine gives a mixture of cis- and trans-3,3,3-trifluoro-1-iodo-NN-bistrifluoromethylprop-1-enylamine which dehydroiodinates readily to 3,3,3-trifluoro-NN-bistrifluoromethylprop-1-ynylamine. Other routes to this latter acetylene, which involve the preparation of 3,3,3-trifluoro-NN-bistrifluoromethylprop-1-enylamine, were also investigated, but these were less satisfactory.