The synthesis of some alk-2-ynylphosphines is described. Alk-2-ynyl halides react with sodium diphenylphosphide in liquid ammonia or tetrahydrofuran, under carefully controlled conditions, to give alk-2-ynylphosphines. In the presence of excess of phosphide diphenylprop-2-ynylphosphine rearranges to give the isomeric allenyl and prop-1-ynyl derivatives. In some cases bromo-derivatives react by nucleophilic substitution on bromine rather than on carbon and the course of these reactions is discussed.