The synthesis and characterization of the new phosphino acetylenes (C6H5)2PC≡CCF3, (C6H5)2PC≡CC(CH3)3, (C6H5)2PC≡CP(C6F5)2, (C6F5)2PC≡CCH3, (C6F5)2PC≡CC6H5, (C6H5)2PC≡CP[N-(C2H5)2]2, the mixed arsine–phosphine (C6H5)2PC≡CAs(C6H5)2 and the arsino acetylene (C6H5)2AsC≡CCF3, are reported.