The microstructure and conformation of highly piezoelectric poly(vinylidene cyanide-co-vinyl formate), prepared by radical copolymerization, were studied by C-13 and two-dimensional H-1 J-resolved n.m.r. spectroscopy, respectively. This copolymer was found to have a highly alternating and stereochemically atactic sequence and a predominantly trans-rich conformation about the main-chain methylene-methine bond in deuterated dimethyl sulfoxide solution. These structural characteristics do not differ greatly from those of other previously reported piezoelectrically active vinylidene cyanide copolymers with vinyl acetate, vinyl benzoate, and vinyl pivalate or from those of piezoelectrically less active vinylidene cyanide copolymers with styrene and methyl methacrylate.